A  PRACTICAL  TREATISE 


ON  THE 


MANUFACTURE  OF  COLORS 


FOR 


PAINTING. 

COMPRISING 

THE  ORIGIN,  DEFINITION,  AND  CLASSIFICATION  OF  COLORS;  THE 
TREATMENT  OF  THE  RAW  MATERIALS;  THE  BEST  FORMULA 
AND  THE  NEWEST  PROCESSES  FOR  THE  PREPARATION 
OF  EVERY  DESCRIPTION  OF  PIGMENT,  AND  THE 
NECESSARY  APPARATUS  AND  DIRECTIONS 
FOR  ITS  USE;  DRYERS;  THE  TESTING, 
APPLICATION,  AND  QUALITIES 
OF  PAINTS,  ETC.  ETC. 

BY 

MM.  RIFPAULT,  VERGNAUD,  AND  TOUSSAINT. 

Revised  and  Edited  by  M.  F.  MALEPEYRE. 

TRANSLATED  FROM  THE  FRENCH 
BY 

A.  A.  FESQUET, 

CHEMIST  AND  ENGINEER. 


ILLUSTRATED  BY  EIGHTY  ENGRAVINGS. 


PHILADELPHIA: 
HENRY    CAREY  BAIRD, 
INDUSTRIAL  PUBLISHER, 
406  WALNUT  STREET. 

LONDON: 
SAMPSON  LOW,  MARSTON,  LOW  &  SEARLE, 
CROWN  BUILDING,  188  FLEET  STREET. 

1874. 


Entered  according  to  Act  of  Congress,  in  the  year  1874,  by 
HENRY   CAREY  BAIRD, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington.    All  rights  reserved. 


PHILADELPHIA : 
COLLINS  PRINTER, 

705  Jayne  Street. 

-GETTV  ClHUR 


PREFACE. 


The  volume  here  presented  to  the  American  pub- 
lic, derived  as  it  is  from  the  last  and  greatly  im- 
proved Paris  edition  of  the  well-known  work  of  MM. 
Riffault,  Vergnaud,  and  Toussaint,  edited  by  M.  F. 
Malepeyre,  is  believed  to  be  by  far  the  most  tho- 
rough and  complete  treatise  upon  the  important  sub- 
ject which  it  considers,  ever  published  in  the  English 
language. 

It  comprises  some  account  of  those  pigments  now 
known  to  have  been  used  by  the  ancients ;  the  prin- 
ciples of  color  as  developed  by  Chevreul ;  thorough 
descriptions  of  the  nature  and  properties  of  the  raw 
materials  used,  and  the  processes  and  machinery  for 
the  manufacture  of  an  immense  variety  of  pigments; 
the  combinations  necessary  in  the  compounding  of 
those  colors,  hues,  and  tones  which  are  the  results 
of  the  mixture  of  colors ;  practical  information  as  to 
dryers ;  and  a  variety  of  analyses  and  tests  of  pig- 
ments, and  much  other  useful  information. 

The  translator  has  devoted  great  care  and  attention 
to  the  faithful  rendering  of  the  production  of  the 
French  authors,  while  the  publisher  has  at  the  same 


iv 


PREFACE. 


time  endeavored  to  present  the  book  in  a  neat  and 
creditable  form,  and  both  trust  that  their  eiforts  will 
be  appreciated,  and  that  the  book  will  meet  with  a 
rapid  and  extended  sale  as  well  in  Great  Britain  as 
in  the  United  States. 

Philadelphia,  June  25,  1874.  , 


CONTENTS. 


Introduction  on  the  Colors  employed  by  the  Ancients. 

PAGE 


White  used  by  the  Egyptians  and  Romans  .  .  .  .17 
Blacks  and  Browns         .         .  .         .  .         .  .19 

Yellows  20 

Red  used  by  the  Egyptians         .  .  .         .  .  .21 

Red  employed  by  the  Greeks  and  Romans        .         .  .  .21 

Grecian  Purple,  also  called  Tyrian  Purple       .  .  .  .25 

Blues         .........  26 

Greens       .........  30 


CHAPTER  I. 
Origin,  Definition,  and  Classification  of  Colors. 

SECTION  I. 

Origin  of  Colors. 

SECTION  II. 
Determination  and  Definition  of  Colors. 

section  III. 
Physical  Effects  of  Colors. 
Colors  of  the  Rays  of  the  Solar  Spectrum 
Primary  Colors  ..... 
Complementary  Colors  .... 
Contrast  of  Tone  ..... 
Contrast  of  Colors  .... 

SECTION  IV. 
Classification  of  Colors. 


Primary  Colors     .   •  .         .         .  .         .         .  .48 

Binary  Colors       .  .         .         .         .         .         .  .48 

Binary  Mixed  Colors  .......  48 

Tertiary  Colors  (pure)  .  .  .         .         .  .  .49 

Tertiary  Colors  (mixed)  .         .         .         .         .         .  .49 


.  46 

.  46 

.  46 

.  46 

.  47 


vi 


CONTENTS. 


SECTION  V. 
General  Method  of  preparing  Colors. 

CHAPTER  II. 
Manufacture  of  Colors. 

SECTION  I. 
White  Colors.  , 

page 


§  1.  Whites  with  Lime  Basis     .  .  .         .  .  .53 

1st.  Carbonate  of  Lime  .         .  .  .  .  .53 

2d.  White  of  Sulphate  of  Lime  .  .  .  .  .55 

§  2.  Whites  with  Lead  Basis     .  ,  .  .         .  .55 

1st.  Kremnitz  Process    .  .         .  .       ■  .  .59 

2d.  Holland  or  Dutch  Process  .  .  .  .63 

Analyses — Krems'  White  .         .  .  .70 

Precipitated  White  Lead  of  Magdeburg        .  .  76 

White  Lead  of  Unknown  Manufacture         .  .  76 

Krems'  White  .  .  .  .  .  .77 

White  Lead  prepared  by  the  Author  in  Imitation  of 
the  Holland  Process  .  .  .  .  .77 

3d.  The  French  or  Clichy  Process  of  Thenard  .  .  78 

Preparation  of  the  Oxide  of  Lead         .         .  .80 
Manufacture  of  the  White  Lead  .  .         .  .80 

4th.  Pattinsdn  Process    .  .  .  ,         .  .85 

5th,  Woolrich  Process    .  .  .  .  .  .92 

6th.  Versepuy  Process   .  .  .  .         .  .93 

7th.  Wood,  Benson,  and  H.  Griineberg  Processes      .         .  97 
8th.  Mullin's  Process     .  .  .  .         .  .105 

9th.  Schuzenbach  Process         .  .         .  .  .110 

10th.  Sewell  Process       .         .         .         .  .  .111 

Explanation  of  the  Apparatus     ....  113 

11th.  Crompton  Process   ......  115 

Mode  of  working  the  Apparatus  .         .  .119 

12th.  Gannal  Process      .         .  .         .         .  .125 

13th.  Rostaing  Process     .  .         .  .  .  .126 

14th.  Mulhouse  White  Lead       .  .  .         .  .126 

15th.  Silver  White  or  Light  White        .         .  .  .127 

16th.  Testing  the  Purity  of  White  Leads         .  .  .127 

17th.  Composition  of  White  Leads        ....  134 

18th.  Processes  for  Rendering  the  Manufacture  of  White  Lead 

less  Unhealthy  .  .  .  .  .  .137 

A.  Ward  Machine  for  the  Manufacture  of  White  Lead        .  138 

B.  Apparatus  of  Mr.  Th.  Lefevre  for  pulverizing  White 

Lead  140 


CONTENTS. 


vii 


PAGE 

Casting  of  tlie  Lead  .....  146 
Building  the  Beds  .....  147 

Taking  the  Beds  apart    .  .  .         .         .  148 

Picking  up  .         .  ....  149 

Dry  Grinding  of  Scales  of  White  Lead  .         .  .  149 

Grinding  White  Lead  in  Water  .  .  .150 

Drying  Booms     .  .  .  .         .  .150 

Powdering  Lump  White  Lead    ....  151 

Packing  White  Lead      .  .         .         .  .153 

C.  Safe  Apparatus  of  Mr.  Ozouf       .  .  .  .154 

D.  J.  Poelmann's  Machine  for  Separating  the  White  Lead 

from  the  Metal  ..... 

E.  Precautions  taken  to  render  the  Manufacture  of  White 

Lead  less  Unhealthy  .... 

§  3.  White  of  Basic  Chloride  of  Lead  .... 

§  4.  White  of  Sulphite  of  Lead  .... 

§  5.  White  of  Tungstate  of  Lead  .... 

§  6.  Antimonite  of  Lead  ..... 

§  7.  Antimoniate  of  Lead         .  .         ,         .  . 

§  8.  Antimony  Whites  ...... 

1st.  Antimony  White  of  MM.  Bobierre,  Ruolz,  and  Rousseau 
2d.  Antimony  White  of  MM.  Valle  and  Barreswill  . 
3d.  Antimony  White  of  MM.  Hallett  and  Steuhouse  . 
§  9.  Zinc  White  ....... 

1st.  Manufacture  of  Zinc  White  of  Mr.  Leclaire 

Manufacture  ..... 

Description  of  the  Apparatus 
Mode  of  Operation. — 1.  With  the  ^^etorts 

2.  Air  Furnace  .... 

3.  Reverberatory  Furnace  or  Coke  Oven 

4.  Horizontal  Tubular  Furnace 
2d.  Mode  of  Fabrication  by  Murdoch  . 
3d.  Manufacture  of  Zinc  White  at  Portillon,  near  Tours 

4th.  Snow  White,  Zinc  White,  Hopper  White 
5th.  Saint-Cyr  White  ..... 
6th.  Vitry  White  .  .  .  .        '  . 

7th.  Various  Pigments  obtained  with  Zinc  White 

Azure-White,  Pearl-Gray,  Slate-Gray,  Straw-Yellow 
Stone  Color,  Chamois,  Dark  Chamois,  Lemon,  Gold 
Yellowy  Tint  of  Azure-Blue,  Water-Green,  Grass 
Green,  Olive-Green,  Bronze-Green 
8th.  Various  Processes  for  the  Manufacture  of  Zinc  White 
9th.  Uses  of  Zinc  White,  and  Dryers  . 
10th.  Adulteration  of  Zinc  White 
11th.  Danger  and  Salubrity  of  Zinc  White 
12th.  Use  of  Blende  as  a  Substitute  for  White  Lead  and  Zinc 

White  191 


viii 


CONTENTS. 


PAGE 

§  10.  Baryta  Whites        .         .         .         .         .         .  .192 

1st.  Natural  Sulphate  of  Baryta  .  .         .  .192 

2d.  Artificial  Sulphate  of  Baryta,  Blanc  Fixe  .  .  .193 

'  SECTION  II. 

Blue  Colors. 

§  1.  Prussian  Blue         .         .         .         .         .         .  .199 

1st.  Manufacture  of  Ordinary  Prussian  Blue   .          .          .  200 

First  Process       ......  200 

Second  Process     ......  203 

2d.  Brunnquell  Process  ......  205 

3d.  Karmrodt  Process    ......  219 

Karmrodt's  Experiments  with  Furnace  .         .         .  223 
I.  By  using  1.5  kilogrammes  of  Carbonate  of  Am- 
monia    ......  223 

II.  With  Animal  Substances           .          .         .  223 


III.  With  Animal  Substances  and  the  Alkalized 
Charcoal  of  30  kilogrammes  of  Wood  Char- 
coal, 20  of  Russian  Potash  and  the  Precipitate 
of  4  kilogrammes  of  Sulphate  of  Iron,  and  3 
of  Potash  .         .  .  .  .224 

4th.  Schinz  Process       ......  226 

5th.  Determination  of  the  Value  of  the  Fused  Materials       .  230 
Preparation  of  the  Titrated  Liquor       .         .         ,  234 
Analytical  Operation       .....  234 

6th.  Preparation  of  Prussian  Blue  by  the  Stephens  Process  .  235 
First  Improvement         .....  235 

Second  Improvement      .....  237 

7th.  English  Process  for  the  Manufacture  of  Prussian  Blue  .  239 
§  2.  Paris  Blue    .  .  .  .         .         .  .  .244 

First  Process      .         .  .         .  .  .  .247 

Second  Process   .......  250 

Third  Process     .  .  .         .         .         .  .251 

Fourth  Process    .  .  .  .         .  .  .252 

§  3.  Monthiers'  Blue      .  .  .  .  .  .  .253 

§  4.  Testing  the  Value  of  Prussian  Blue  and  its  Adulterations         .  254 
§  5.  Mineral  Blue,  Antwerp  Blue        .....  256 

§  6.  Thenard  Blue,  or  Cobalt  Blue  (Subphosphate  of  Cobalt)  .  257 
§  7.  Blue  Hydrated  Oxide  of  Copper.    Peligot  Blue  .  .  .261 

§  8.  Blue  of  Manganate  of  Lime.         .....  262 

§  9.  Indigo  264 

§  10.  Blue  Carmine,  Indigo  Carmine,  Blue  of  England  or  Holland     .  268 
§11.  Ultramarine  Blues  .         .         .         .         .         .  .269 

1st.  Real  or  Native  Ultramarine  Blue  ....  270 

Ultramarine-lazulite        .....  270 

Analyses    .         .         .  .         .         .  .272 


CONTEXTS.  ix 

PAGE 

2d.  Artificial  Ultramarine         ,         .         .         .         .  274 
Analyses  275 

A.  Guimet  Process        ......  277 

B.  Gmelin  Process        .  .         .         ,         .  .  278 

C.  Tiremon  Process      .         .  .  .  .  .280 

D.  Weger  Process         .         .         ,  .         .  .281 

Ultramarine  for  Printing  .  .         ,  .         .  282 

E.  Pruckner  Process      ......  283 

F.  Winterfield  Process  .  .         .         .         .  .288 

G.  Brunner  Process       ......  289 

Choice  of  the  Raw  Materials       .  .         .  .290 

Analysis  of  Ultramarine  .         .  .  .  .  296 

H.  Dippel  Process         .         .         ,         .         .  .300 

I.  Habich  Process         ......  301 

K.  Gentele  Processes     ......  304 

1.  Manufacture  of  Ultramarine  Green    .         .  .  805 

2.  Manufacture  of  Ultramarine  Blue     .  .  .  318 
L.   Furstenau  Process    ......  323 

M.  White  Ultramarine  .  .         .         .         .  .327 

N.  Trial  and  Analysis  of  Ultramarines  .         .  .  329 

1st.  Artificial  Ultramarine  of  the  First  Quality  .  .  332 

2d.  Inferior  Qualities      .  .         .         .  .332 

Biichner's  Tests    .  .         .         .  .  .333 

(a.)  Resistance  to  the  Action  of  Alum  .  .  333 

(b.)  Trial  of  the  Coloring  Power       ,  .  .334 

(c.)  Trial  of  the  Printing  Power  .  .  .336 
(d.)  Trial  of  the  Glazing  Power        .  .  .337 

(e.)  Trial  for  the  Proportion  of  Gelatine  (size)        .  337 

0.  Composition  of  Ultramarines  ....  339 

3d.  Cobalt  Ultramarine    .....  340 
§  ]  2.  Blue  Ashes.    Lime  Blue.    Copper  Blue.    Mountain  Blue        .  341 

1.  Manufacture  of  Ashes  in  England    ....  342 
II.  Gentele' s  Researches  .....  345 

III.  Distinguishing  Blue  Ashes  of  England  and  of  France       .  350 

IV.  Natural  Color,  called  Mountain  Blue,  Azurite,  and  Arme- 

nian Stone  .......  350 

§  13.  Smalt  ........  351 

§  14.  Cceruleum    .         .         .         .         .  .         .  .354 

§  15.  Litmus        ........  356 

§  16.  Enghsh  Sky  Blue  356 


SECTION  III. 
Yellow  Colors. 

.  358 
.  358 
.  361 


Yellows  in  General 
§  1.  Ochres 

§  2.  Rut  (Rivulet)  Ochre 


X 


CONTENTS. 


PAGE 

§  3.  Italian  and  Sienna  Earths  ......  361 

§  4.  Vienna  Red.    Antwerp  Red.    Terra  Rosa         .  .  .  363 

§  5.  Mars  Yellows         .......  363 

§  6.  Curcuma  or  Terra  Merita   ......  364 

§  7.  Stil-de-grain  .         .  .  .  .  .  .366 

§  8.  Weld  Lake  ........  368 

§  9.  Lakes  of  Quercitron  and  Yellow  Wood    .  .  .  .371 

§  10.  Chrome  Yellows      .  .  .         .  .         .  .373 

1.  Neutral  Chromate  of  Lead     .....  373 

3.  Basic  Chromate  of  Lead       .  .       ,  .  .         .  375 

3.  Jonquil  Chrome  Yellow  of  Winterfeld       .  .  .  376 

4.  Cologne  Yellow        ......  377 

5.  Chromate  of  Lime      ......  378 

6.  Chromate  of  Baryta    ......  378 

A.  Chrome  Yellow         .  .  .         .         .         .  379 

B.  Chrome  Red  or  Basic  Chromate       .  .  .  .  385 

C.  Greens  by  Mixtures  (Cinnabar  Green,  Chrome  Green)     .  386 
§  11.  Various  Chromates  .......  387 

1.  Chromate  of  Zinc      ......  388 

Wagner's  Analysis  .....  391 

3.  Chromate  of  Baryta    ......  391 

3.  Orange-red  Sulphide  of  Antimony    ....  393 

4.  Mixed  or  Compound  Colors  .....  393 

5.  Lemon  Yellow  .  .  .  .         .  .395 

6.  Pale  Yellow  395 

§18,  Basic  Chromate  of  Tin,  Mineral  Lake      ....  395 

§  13.  Naples  Yellow        .  .  .  .  .         .  .397 

§  14.  Cadmium  Yellow    .  .  .  .  .         .  .400 

§  15.  Yellow  of  Antimony  and  Zinc      .....  401 

§16.  Turner  Yellow.    Kassler  Yellow..   Cassel  Yellow.  Montpellier 

Yellow.    Verona  Yellow.    Mineral  Yellow    .  .  .  403 

§  17.  Mineral  Straw -yellow        .  .  .  .  .  .406 

§  18.  Mineral  Turbith      .  .  .  .  .  .  .406 

§  19.  Orpin  or  Orpiment.    Yellow  Sulphide  of  Arsenic.    Yellow  Re- 
algar.       .  .  .  .  .  .  .         .    407  • 

§  30.  Arsenite  of  Lead     .  .  .  .  .         .  .409 

§  31.  Massicot.    Litharge  .         .  .  .         .  .409 

§  33.  Iodide  of  Lead        .......  410 

§33.  Uranium  Yellow     .  .  .  .  .         .  .411 

§34.  Gamboge  417 

§  35.  Jaune  Indien  (Indian  Yellow).    Purree  ....  417 

§  36.  Aurum  Mussivum.    Mock  Gold.    Mosaic  Gold.    Cat's  Gold. 

Painter's  Bronze,  etc.      ......  430 

§  37.  Nankin  Yellow       .  .  .         .  .         .  .431 

§  38.  Chlorophyl  .  .         .  .         ,  .         .         .    431  ^ 


CONTENTS.  xi 

SECTION  IV. 
Red  Colors. 

PAGE 

§  1.  Red  Ochre    .  433 

§  2.  Colcothar.    English  Red  or  Rouge         ....  424 

§  3.  Armenian  Bole.    Ochreous  Clay.    Lemnos  Earth.  Oriental 

Bole.    Red  Bole  .         .  .  .         ,  .  .425 

§  4.  Iron  Minium  .         .  .         .         .         .         .  425 

§  5.  Red-Brown  .  .  .         .  .  .         .  .426 

§  6.  Red  Lead  or  Minium         .  .  .  .         .  .  426 

§  7.  Orange  Mineral       .  .  .         .  .         .  .  428 

§  8.  Realgar,  or  Ruby  of  Arsenic         .....  429 

§  9.  Cinnabar  and  Vermilion     ......  430 

1.  Manufacture  by  the  Dry  Way         .         .  .  .  430 

2.  Manufacture  by  the  Wet  Way         .         .         .  .431 

A.  Kirchoff  Process        .  .  .         .         .  .432 

B.  Brunner  Process        .......  432 

C.  Jacquelin  Process      ......  433 

D.  Firmenich  Process     ......  434 

§  10.  Iodide  of  Mercury   .  ....  ...  439 

§11.  Chromates  of  Mercury      ......  439 

§  12.  Chromate  of  Copper.    Maroon-red  .....  440 

§  13.  Chromate  of  Silver.    Purple-red   .  .         .  .  .440 

§  14.  Sulphide  of  Antimony.    Vermilion  of  Antimony  .  .  441 

1.  Preparation  of  the  Chloride  of  Antimony     .  .         .  446 

2.  Preparation  of  the  Hyposulphite  of  Lime     .  .  .  447 

3.  Preparation  of  Vermilion  of  Antimony      .  .  .  448 

4.  Properties  of  the  Vermilion  of  Antimony    .  .  .  452 
§15.  Sulpho-antimonite  of  Barium        .....  453 

§  16.  Cobalt  Pink  .454 

§  17.  Arseniate  of  Cobalt,  Metallic  Lime  .....  455 

§18.  Purple  of  Cassius    ........  455 

§  19.  Madder  Lake  ........  458 

1.  Robiquet  and  Colin  Process  ....         .  460 

2.  Persoz  Process  ......  461 

3.  Lefort  Process  ......  462 

4.  Khittel  Process         .  .         .         .  .  .463 

5.  Lake  of  Garanceux    ......  567 

6.  Sacc  Process  .......  469 

7.  Kopp  Process  .......  469 

8.  Adulteration  of  Lakes  .....  471 

A.  Red  and  Pink  Lakes    .....  471 

Santaline         ......  472 

Lakes  of  Brazil  Wood. — First  Process         .         .  472 
Venice  Lake,  ball  shape. — Second  Process  .  .  472 

Brazil  Lake. — Third  Process  ....  472 

Carmine  Lake  ......    475-  (h- 


4 

xii  CONTENTS. 

PAGE 

B.  Voilet  Lakes     .         .         .         .         .  .473 

Campeacliy  Lakes       .....  473 

Alkanet           ......  474 

Orchil   .  .  .  .  .         .  .474 

Prussian  Blue  ......  474 

C.  Black  Lakes  •        .  474 

Charcoal  and  Lampblack       ....  474 

Black  Campeachy  Lakes        ....  475 

Lake  with  Cochineal  Basis     ....  475 

Black  Sumach  Lake,  etc.       .  '       .          .          .  475 

§  20.  Violet,  Chocolate,  Brown,  and  Bed  Lakes  of  Rhamnoxanthin 

and  Elder  Berries           ......  475 

§  2L  Madder  Carmine     .......  477 

§  22.  Lake  of  Red  Woods   477 

§  23.  Vegetable  Violet     .  .  .  .  .  .  .484 

§  24.  Carthamus  Red.  Carthamin.   Carthamic  Acid.  Vegetable  Red. 
Spanish  Red.    Red  in  Plates.    Portuguese  Red.    Leaf  Red. 

Chinese  Rouge  for  the  Face      .....  484 

§25.  Indian  Red   486 

§  26.  Cochineal  Carmine  .         .         .         .         .         .  .487 

1.  Process  of  the  Old  French  EncyclopedJa    .         .         .  489 

2.  Ordinary  Process       ......  490 

3.  Chinese  Process        ......  490 

4.  German  Process        ......  491 

5.  Process  by  Cream  Tartar      .....  491 

6.  Process  with  Wool  and  Formation  of  a  Lake        .         .  491 

7.  Wood  Process          ......  492 

8.  Grelley  Process         .         .         .         .         .  .492 

§  27.  Carmine  Lake.    Paris  Lake.    Vienna  Lake       .         .         .  493 

§  28.  Ammoniacal  Cochineal      ......  494 

§  29.  Red  and  Violet  from  Archil   495 

§  30.  Perchloride  of  Chromium   499 

§31.  Chrome  Red   500 

SECTION  V. 
Brown  and  Black  Colors. 

I.  BROWNS. 

§  1.  Mars  Browns         .......  500 

§  2.  Iron  Minimum        .......  501 

Analyses  ........  502 

Employment  of  Iron  Minimum  .....  503 

§  3.  Vandyke  Brown      .  .  .  .  .  .  .504 

§  4.  Manganese  Brown  .......  505 

§  5.  Brown  of  Manganate  of  Lead        .....  506 

§  6.  Prussian  Brown      .......  506 


* 


CONTENTS.  xiii 

PAGE 

§  7.  Red-Brown  ........  507 

§8.  Gilt-Brown  '         .  .507 

§  9.  Chicory-Brown       .      "    .  .         .         .  .  .507 

§  10.  Ulmin-Brown         .  .         .  .         .  .  .507 

§  11.  Bistre  508 

§  12.  Bitumens  or  Asphaltum     ......  509 

Bitumen  Naphtha  ......  509 

Bitumen  of  Judea  or  Asphaltum  ....  509 

Bitumen  or  Retin  Asphaltum     .....  509 

§  13.  Sepia  510 

§  14.  Umber         .         .  511 

§  15.  Sienna  Earth  .  .  .  .  .  .  .511 

§  16.  Cologne  and  Cassel  Earths  .  .  .  .  .512 

§  17.  Puce  with  Chromate  of  Manganese         ....  512 

11.  BLACKS. 

A.  Mineral  Blacks. 

%  1.  Schist  or  Shale  Black         .  .         .  .         .  .512 

§  2.  Bituminous  Coal  Black      .  .  .  .  .  .513 

^  3.  Black  of  Chromate  of  Copper       .....  514 

§4.  Ebony  Black  515 

B.  Vegetable  Blacks. 

§  5.  Peach-stone  Black  .......  515 

§  6.  Fusain  (Spindle  Tree,  Prickle  Wood)  Black       .  .  .  515 

§  7.  Grape-vine  Black    .  .         .  .  .  .  .515 

§8.  Cork  Black  516 

§  9.  German  Black        .         .  .  .  .  .  .516 

§  10.  Frankfort  Black      .  .  .  .  .         .  .516 

§  11.  Lampblack  517 

First  Process. — Resin  Black      .....  518 

Second  Process. — Tar  Black      .....  519 

Third  Process. — Oil  or  Lampblack       ....  521 

§  12.  Chrome  or  Aniline  Black   .         .  .  .         .  .524 

§  13.  Various  Blacks       .  .         .  .  .  .  .225 

§  14.  Inks  528 

C.  Animal  Blacks. 

%  15.  Bone  Blacks  .  .  .  .         .         .  .529 

§  16.  Ivory  Black  .  .  .  .  .         .  .530 

§17.  Candle  Black  530 

§  18.  Prussian  Black       .         .         .         .  .         .  .531 

§  19.  China  or  India  Ink  .  .         .         .         .         .  .531 


xiv 


CONTENTS. 


SECTION  VI. 
Green  Colors. 

PAGE 

§  1.  Green  Verona  Earth         ......  532 

§  2.  Malachite     .  .  .  .    '     .  .         .  .534 

§  3.  Iris-Green     ........  534 

§  4.  Sap-Green    .  .  .  .  .  .        '  .  .534 

§  5.  Picric  Acid  Green   .....  .         .  537 

§  6.  Bremen  Green.    Bremen  Blue.     Verditer  Blue  and  Green      .  538 
§  7.  Brunswick  Green    .  .  .  .       '  .  .  .  543 

§  8.  Scheele's  Green       .  .     ♦     .  .  .  .  .543 

^  9.  Scliweinfurt  Green  .......  545 

First  Process       .  .  .  .  .  .         .  545 

Second  Process    .  .  .  .  .  .         .  545 

Third  Process      .  .  .  .  .  .  .546 

Fourth  Process  .  .  .         .  .  .  546 

§  10.  Mittis  Green.    Vienna  Green.    Kirchberger  Green       .  .  547 

§  11.  Green  Ashes  .......  548 

§  12.  German  Green  without  Arsenic     .....  548 

§  13.  Erlaa  Green  .  .  .  .  .  .  .549 

§  14.  Mineral  Green        .  .  .  .  .  .  .  549 

§  15.  Paul  Veronese  Green         ......  550 

§  16.  English  Green        .  .  .  .  .  .  .550 

§17.  Neuwied  Green       .  .  .  .  .         .  .550 

§18.  Milory  Green.    Silk  Green.    Green  Cinnabar.    Leaf  Green      .  551 
§19.  Green  of  Stannate  of  Copper         .....  552 

§  20.  Eisner  Green  ....  .  .  .  553 

§  21.  Green  Cinnabar      .......  553 

§  22.  Green  Lakes.    Vegetable  Green.    Grass-green.    China  Green  .  554 
§  23.  Mineral  Green  Lake  .  .  .  .  .  .556 

§  24.  Rinmann  Green.    Cobalt  Green.    Zinc  Green     .  .         .  556 

§  25.  Chrome  Green        .  .  .  .  .  .  .  561 

§  26.  Emerald  Green        .  .  .  .  .  .  .563 

§  27.  Titanium  Green      .  .  .        ' .  .  .  .568 

§  28.  Green  Ochre  .  .  .  .  .         .  .571 

§  29.  Green  Ultramarine  .  .  .  .  .         .  .571 

§30.  Verdigris  572 

§31.  Crystallized  Verdet.    Distilled  Green.    Crystals  of  Venus        .  573 


SECTION  VII. 

Colors  from  Sulphate  of  Zinc 

Delicate  Light  Yellows,  called  Roman  Yellows 
Chamois  Yellows  ..... 
Yellow  Chamois    .  . 

Dark  Chamois  ..... 
Gold  Yellows  ..... 


.  574 

.  574 

.  574 

.  575 

.  575 


CONTENTS.  XV 

PAGE 

Dark  Gold-Yellows  575 

Greens  resembling  Sclieele's  Greens      .....  575 

Dark  Greens         ........  575 

Yellowish-Greens  ........  575 

Grays        .........  575 

Bronzes      .........  575 

Dark  Bronzes       ........  575 

Pinks   .         .  .575 

Dark  Pinks  .         .  575 

Whites   .  .576 


CHAPTER  III. 
Drying  and  Adherence  of  Colors. 

SECTION  I. 
Dryer  for  Zinc  White. 

SECTION  II. 
Drying  Oils. 

SECTION  III. 
Powdered  Dryer  of  Guynemer. 

SECTION  IV. 
Various  Dryers.    Zumatic  Dryer 

1.  Benzoate  of  Cobalt,  and  Benzoate  of  Manganese 

2.  Borate  of  Cobalt  ..... 

3.  Employment  of  Resins  .... 

4.  Borate  of  Manganese  ..... 

Zumatic  Lake  ..... 

SECTION  V. 

Spreading,  Drying,  and  Adhering  Properties  op  Oil  Paints. 
Chevreul's  Memoir  on  Oil  Painting       .....  588 

CHAPTER  ly. 
Bronzing. 

SECTION  I. 

Real  Bronze,  Color  which  it  acquires  in  the  Air. 


.  583 

.  584 

.  584 

.  585 

.  587 


SECTION  11. 
Various  Bronze  Compositions  for  Metals. 


xvi 


SECTION  III. 
Recipe  for  the  Ordinary  Bronze  of  the  Founders. 

SECTION  IV. 
Mode  of  Applying  the  Bronzing  Mixtures. 

SECTION  V. 

Mode  of  giving  the  Proper  Bronze  Coloration,  without 
Lampblack. 

SECTION  VI. 
Bronzing  of  Gun  Barrels. 

SECTION  VII. 
Bronzing  Plaster  of  Paris. 

SECTION  VIII. 
Green  Bronze. 


APPEi^DIX. 

PAGE 


Mill  for  Grinding  Colors  .......  604 

Mill  for  Dry  Indigo         .         .         .         .         .         .  .607 

Improvements  in  the  Manufacture  of  Oils,  Varnishes,  and  Colors,  by 

MM.  H.  Bessemer  and  J.  S.  C.  Heywood      ....  608 

Description  of  an  English  Mill  for  Grinding  Colors      .         .         .  626 
Hermann's  Mill     ........  639 

The  Metric  System  of  Weights  and  Measures    ....  631 

Tables  showing  the  Relative  Values  of  French  and  English  Weights 

and  Measures,  etc.        .......  633 

Index       .         .         .         .         .         .         .         .  .641 


MANUFACTURE 

OF 

COLORS  FOR  PAINTING. 


INTRODUCTION  ON  THE  COLORS  EMPLOYED  BY 
THE  ANCIENTS. 

Several  ancient  writers,  and  especially  Theo- 
phrastes,  Pliny,  and  Vitruvius,  have  transmitted  to  us 
interesting  data  regarding  the  colors  known  in  their 
times,  and  which  were  so  skilfully  employed  for 
adorning  their  public  and  private  buildings.  In  our 
time,  the  chemists,  Sir  Humphry  Davy,  Chaptal,  and 
"Vauquelin,  and  the  painter,  Merimee,  have  analyzed 
these  materials,  and  have  also  examined  the  modes  of 
preparing  and  applying  them.  We  think  that  it  will 
be  found  useful  to  reproduce  here  a  few  extracts  from 
these  important  researches,  in  order  better  to  appre- 
ciate the  progress  of  this  branch  of  chemistry  since 
the  days  of  old. 

White  used  hy  the  Egyptians  and  Romans, — The 
white  employed  by  the  Egyptians  is  remarkably  fast 
and  well  preserved.  Merimee  thinks  that  it  is  sim- 
ply plaster  of  Paris  (sulphate  of  lime)  mixed  with 
a  certain  glue  or  mucilage,  the  nature  of  which  he 
could  not  ascertain. 

In  certain  vessels  discovered  in  the  excavations  of 
the  baths  of  Titus,  at  Pome^  mrious  pigments  were 
found,  which  were  analyzed  by  Davy,  and  which  cor- 
2 


18  MANUFACTURE  OF  COLORS. 

responded  with  those  of  the  fresco  paintings  of  that 
palace,  or  those  of  fragments  of  stucco  work  discov- 
ered in  the  ruins. 

The  same  chemist  ascertained  that,  in  general,  the 
ancient  whites  were  soluble  with  effervescence  in 
the  acids,  and  presented  the  characteristics  of  car- 
bonate of  lime. 

The  whites  contained  in  the  vases  of  the  baths  of 
Titus,  where  many  mixed  colors  were  found,  appeared 
to  Davy  as  being  of  different  kinds,  that  is,  very 
finely  pulverized  chalk,  another  white  slightly  yel- 
lowish, like  cream,  and  perfectly  comminuted  clay. 
Moreover,  none  of  the  whites  examined  by  this 
chemist,  whether  in  these  baths  or  in  any  monument 
of  Roman  antiquity,  contained  a  trace  of  white  lead, 
although  Pliny  and  Yitruvius,  especially  the  latter, 
claim  that  white  lead  was  a  commonly  used  paint, 
produced  by  the  action  of  vinegar  upon  lead. 

In  all  Egyptian  pictures,  whether  made  upon  wood 
or  canvas,  the  priming  coat  is  always  some  kind  of 
a  white,  and  the  colors  applied  afterwards,  although 
opaque,  are  somewhat  wanting  in  depth  and  bright- 
ness, on  account  of  a  certain  transparency  in  the 
groundwork.  What  Avas  the  nature  of  the  size 
employed,  is  an  important  question,  because  these 
pictures  were  not  cracked,  as  are  so  many  of  our  own 
old  ones.  Egypt  possesses  mimosa  trees,  which  pro- 
duce a  gum,  and  as  gelatin  glue  was  known,  the  colors 
may  have  been  sized  with  these  two  substances  ;  but 
Merimee  supposes  that  a  more  supple  material,  like 
gum  tragacanth,  or  any  similar  mucilage,  was  pre- 
ferred. 

With  what  tools  were  these  pigments  applied  ?  The 
answer  to  this  question  seems  obvious,  since  the 


INTRODUCTION^. 


19 


invention  of  the  brush  or  pencil  is  so  natural,  that  it 
cannot  have  escaped  the  attention  of  the  Egyptians. 

Blacks  and  Browns. — Davy  found  in  several  places 
fragments  of  stucco  painted  black.  By  several  tests, 
he  ascertained  that  acids  and  alkalies  were  without 
action  upon  the  colors,  but  that  they  burned  with 
nitre,  and  had  all  the  properties  of  a  pure  carbona- 
ceous substance. 

In  the  vessels  filled  with  mixed  paints,  which  we 
have  already  mentioned,  Davy  found  no  black,  but 
various  kinds  of  browns — one  had  the  color  of  to- 
bacco ;  another  was  a  dark  red-brown ;  and  a  third 
was  a  dark  olive-brown.  The  former  two  were  ochres 
which,  very  likely,  had  been  calcined  at  various 
degrees ;  the  third  yielded  oxides  of  manganese  and 
of  iron,  and  produced  vapors  of  chlorine  when  treated 
by  hydrochloric  acid. 

"  All  the  ancient  authors,"  says  Davy,  "describe 
the  artificial  blacks  of  Greece,  or  Rome,  as  carbona- 
ceous substances,  manufactured  from  burned  resins, 
giving  a  kind  of  lampblack,  or  from  the  calcination 
of  ordinary  soot,  or  of  wine  lees.  Pliny  asserts  that 
a  natural  fossil  black  is  found,  and  also  another  pre- 
pared from  an  earth  having  the  color  of  sulphur."  It 
is  probable,  according  to  Davy,  that  these  substances 
are  manganese  and  iron  ores. 

"  It  is  evident  that  the  ancients  were  cognizant  of 
manganese  ores,  from  their  paintings  on  glass." 
Davy  examined  two  samples  of  purple  glass  of  Ro- 
man manufacture  ;  and  both  were  colored  with  man- 
ganese oxide.  Pliny  speaks  of  various  brown  ochres, 
one  especially,  which  he  calls  cicerculum,  coming 
from  Africa,  and  which  probably  contains  manga- 
nese.   Theophrastes  mentions  a  mineral  substance 


20 


MANUFACTURE  OF  COLORS. 


which  takes  fire  when  oil  is  poured  upon  it,  a  pro- 
perty which,  according  to  Davy,  belongs  to  no  other 
actually  known  mineral  substance,  except  a  manga- 
nese ore  found  in  Derbyshire. 

The  browns,  in  the  pictures  of  the  baths  of  Li  via, 
and  of  the  Aldobrandini  "Wedding,  are  considered  by 
Davy  as  mixtures  of  ochres  with  blacks.  Those  of 
the  Aldobrandini  "Wedding  yield  iron  when  treated  by 
hydrochloric  acid,  but  the  dark  shades  are  unacted 
upon  by  the  acid  or  alkaline  solutions. 

Yellows, — Davy  discovered,  in  a  room  of  the  baths 
of  Titus,  a  large  earthenware  pot,  holding  a  large 
quantity  of  yellow  paint,  which,  after  analysis,  was 
found  to  be  a  mixture  of  yellow  ochre  and  chalk 
(carbonate  of  lime).  There  were  in  the  same  vessel 
three  different  kinds  of  yellow,  two  of  which  were 
yellow  ochre  mixed  with  variable  proportions  of 
chalk,  and  the  third  one  yellow  ochre  mixed  with  red 
lead. 

The  yellow  most  esteemed  by  the  ancients  was  the 
ochre  of  Athens.  Vitruvius  asserts  that  at  his 
epoch  the  mine  was  abandoned. 

According  to  Davy,  the  ancients  possessed  two 
other  paints  which  were  yellow  or  orange — the  auri 
pigmentum,  the  color  of  which  resembles  gold,  and 
which  appears  to  be  orpiment  (sulphide  of  arse- 
nic) ;  and  a  pale  sandaraca,  which  Pliny  asserts  to 
be  found  in  gold  and  arsenic  veins,  and  which  was 
imitated  at  Rome  by  a  partial  calcination  of  white 
lead.  From  what  Pliny  says,  Davy  infers  that  the 
lightest  kind  of  orpiment  resembles  sandaraca,  and 
that  another  paint,  called  sandaraca  by  the  Romans, 
was  of  a  bright  yellow,  like  that  of  the  beak  of  the 
blackbird. 


INTRODUCTION. 


21 


Davy  saw  no  example  of  the  use  of  orpiment  in 
old  fresco  paintings.  A  deep  yellow,  somewhat 
orange,  and  which  covered  a  piece  of  stucco  work, 
was  a  mixture  of  litharge  and  red  lead.  This  chemist 
considers  that  it  is  very  probable  that  the  ancients 
employed  several  lead  colors,  such  as  massicot  (lith- 
arge), white  and  red  leads. 

The  yellows  of  the  Aldobrandini  Wedding  are  en- 
tirely ochres.  Davy  also  examined  the  colors  of  a 
pretty  painting  upon  the  walls  of  a  house  of  Pompeii, 
and  ascertained  that  they  were  made  of  yellow  and 
red  ochres. 

An  examination  of  the  Egyptian  collection  of 
Passalaqua,  made  by  a  commission  of  celebrated 
French  chemists,  under  the  direction  of  Merimee, 
demonstrated  the  fact  that  among  the  colors  em- 
ployed by  the  Egyptians  there  are  two  kinds  of  yel- 
low ;  one,  and  the  most  usual,  is  nothing  else  than  a 
light  yellow  ochre  abundantly  found  in  the  vicinity 
of  beds  of  iron  ore.  The  other,  lighter  and  brighter, 
was  a  sulphide  of  arsenic  (orpiment).  This  latter 
substance  may  be  produced  artificially,  but,  as  it  is 
also  found  as  a  mineral,  it  is  probable  that  it  has 
been  employed  in  this  state. 

Bed  used  hy  the  Egyptians. — The  red  employed  in 
the  fine  collection  of  Passalaqua  is,  the  greater  part 
of  it,  a  red  ochre  obtained  by  the  calcination  of  yel- 
low ochre.  Vitruvius  asserts  that  a  fine  red  ochre 
was  obtained  from  Egypt. 

It  is  not  improbable  that  vermilion  may  have  been 
employed  in  some  places.  Cinnabar  was  known 
in  India  from  the  earliest  ages,  and  the  Egyptians 
may  have  obtained  it  by  trade. 

Bed  employed  hy  the  Greeks  and  Boman^, — Among 


22 


MANUFACTURE  OF  COLORS. 


the  substances  contained  in  a  large  earthenware  vase 
filled  with  colors  mixed  with  clay  and  lime,  and 
found  in  an  open  room  of  the  baths  of  Titus,  Davy 
found  different  kinds  of  reds.  One  was  bright, 
and  with  an  orange  tinge ;  another  was  a  pale  red ; 
and  the  third  was  purplish.  The  first  one,  on  ex- 
posure to  the  heat  of  an  alcohol  lamp,  became  darker 
and  even  fused  when  the  blowpipe  blast  was  applied. 
Further  tests  demonstrated  that  it  was  red  lead. 

The  second  became  black  by  heating,  but  reacquired 
its  former  color  on  cooling.  Calcination  in  a  glass 
tube  proved  that  the  only  volatile  substance  was 
water.  Chemical  tests  demonstrated  that  it  was  an 
iron  oxide. 

The  third  sample,  of  a  purplish-red  color,  was 
treated  in  the  same  manner,  and  was  found  to  be  an 
ochre  of  a  different  color. 

After  examining  the  fresco  paintings  of  the  baths 
of  Titus,  Davy  ascertained  that  all  of  these  colors 
had  been  used ;  the  ochres  especially  for  shadowing 
the  pictures,  and  the  red  lead  for  ornamenting  the 
borders. 

The  same  chemist  found  upon  the  walls  another 
red  of  a  tone  different  from  those  found  in  the  vase ; 
it  was  brighter,  and  had  been  employed  in  several 
rooms.  A  small  quantity  of  this  color,  scraped  from 
the  walls,  and  submitted  to  chemical  tests,  proved  to 
be  vermilion  or  cinnabar,  since  metallic  mercury  was 
obtained  by  calcination  with  iron  filings. 

The  same  color  was  also  found  upon  several  frag- 
ments of  stucco  work. 

In  the  Aldobrandini  "Wedding  all  the  reds  are 
ochres.  These  reds,  tested  with  acids,  alkalies,  and 
chlorine,  showed  neither  red  lead  nor  vermilion. 


INTRODUCTION. 


23 


'Red  lead,  says  Davy,  was  known  by  the  Greeks 
and  Romans.  According  to  Pliny  this  paint  was 
accidentally  discovered  in  a  fire  which  took  place  at 
the  Piraeus,  near  Athens.  White  lead  exposed  to  that 
fire  was  transformed  into  red  lead,  and  the  process 
was  imitated  in  manufactures. 

Theophrastes,  Vitruvius,  and  Pliny  describe  several 
red  earths  used  for  painting.  The  earth  from  Sinope, 
that  of  Armenia,  and  African  ochre  produced  a  red 
paint  by  calcination. 

Cinnabar  or  vermilion  was  called  minium  by  the 
Eomans.  "  Theophrastes,"  says  Davy,  "  asserts  that 
it  was  discovered  by  the  Athenian  Callias,  in  the 
349th  year  of  Rome.  It  was  prepared  by  lixiviating 
silver  ores." 

Yermilion,  according  to  Pliny,  was  always  highly 
esteemed  by  the  Romans,  and  its  value  rose  so  high 
at  one  time  that,  to  prevent  a  further  increase,  the 
government  fixed  its  price. 

Davy  found  in  the  baths  of  Titus  another  broken 
vessel,  filled  with  a  light  pink  color,  which  faded  by 
exposure  to  the  air  down  to  a  cream  color ;  but  the 
unexposed  parts  had  a  lustre  like  carmine. 

After  several  experiments  this  learned  chemist  as- 
certained that  it  was  composed  of  silica,  alumina, 
and  lime,  with  no  other  mineral  substance  but  a 
slight  proportion  of  oxide  of  iron.  Heated  with 
oxygen  in  a  glass  tube,  this  color  did  not  burn  and 
became  somewhat  red.  The  gas  escaping  from  the 
tube,  being  passed  through  lime-water,  gave  a  pre- 
cipitate of  carbonate  of  lime.  Another  portion  of 
color  was  also  mixed  with  chlorate  of  potassa  and 
heated  in  a  small  glass  retort;  when  fusion  took 


24 


MANUFACTURE  OF  COLORS. 


place  there  was  a  slight  combustion,  and  the  escaping 
gas  precipitated  lime-water. 

It  appears  from  these  experiments  that  this  color- 
ing substance  was  a  compound  with  some  material 
of  animal  or  vegetable  origin.  Davy  put  some  of  it 
upon  a  heated  iron,  and  there  was  scarcely  any  smoke, 
but  a  slight  smell  resembling  that  of  hydrocyanic 
(prussic)  acid. 

When  caustic  potassa  was  melted  with  this  color, 
the  vapors  had  no  ammoniacal  smell,  although  there 
was  a  light  cloud  in  the  presence  of  hydrochloric 
acid ;  "  but,"  Davy  says,  "  this  is  far  from  being  an 
evident  proof  of  the  presence  of  animal  matter." 
This  chemist  made  a  comparison  of  this  color  with 
the  vegetable  lake  made  from  madder,  and  an  animal 
lake  made  from  cochineal  at  the  same  degree  of  dilu- 
tion and  fixed  upon  alumina.  The  madder  lake, 
dissolved  in  concentrated  hydrochloric  acid,  recovered 
its  color  by  the  addition  of  alkalies,  whereas  the  same 
results  did  not  take  place  with  the  old  color.  The 
solution  of  madder  lake  in  diluted  hydrochloric  acid 
became  of  a  fallow  brown  after  the  addition  of  per- 
chloride  of  iron,  whereas  there  was  no  change  of 
color  with  the  old  lake.  The  latter  and  that  from 
cochineal  became  darker  in  weak  alkalies,  and 
brighter  in  weak  acids.  There  was,  however,  this 
difference;  the  old  lake  was  more  easily  destroyed 
by  concentrated  acids.  Like  animal  and  vegetable 
lakes,  it  was  immediately  destroyed  by  a  solution  of 
chlorine. 

The  smoke  produced  by  the  cochineal  lake,  melted 
with  caustic  potassa,  was  greater,  and  there  was  a 
strong  ammoniacal  smell.  The  combustion  of  the 
madder  and  cochineal  lakes,  in  oxygen,  was  not  more 


INTRODUCTION. 


25 


vivid  in  appearance  than  that  of  the  old  lake.  Davy 
ascertained  that  the  loss  in  weight  of  the  latter  by 
combustion,  was  about  one-thirtieth,  made  up  for  the 
greater  part  of  the  water  combined  with  the  clay  of 
that  pigment.  This  fact  prevented  Davy  from  deter- 
mining its  composition  by  the  process  of  ultimate  de- 
composition, since  the  results  could  not  be  certain. 

From  all  these  experiments,  Davy  thinks  that  it  is 
impossible  to  determine  whether  this  lake  is  of  vege- 
table or  animal  origin,  and  he  adds  :  If  it  is  of  ani- 
mal origin,  it  may  be  Tyrian  or  marine  purple,  and 
this  question  may  possibly  be  solved  by  making  com- 
parative experiments  with  the  purple  shell." 

Davy  could  find  no  instance  where  this  lake  had 
been  employed  in  the  old  fresco  paintings.  The  pur- 
ple-reds of  the  baths  of  Titus  were  mixtures  of  red 
ochres  and  copper  blues. 

Orecian  Purjple^  also  called  Tyrian  Purple. — The 
Ostrum  of  the  Romans,  and  the  purple  of  the  Greeks, 
was  considered  by  these  nations  the  finest  color,  and 
it  was  extracted  from  a  shell.  Vitruvius  asserts  that 
this  color  varied  with  the  countries  from  which  the 
shell  was  exported.  That  from  the  northern  coun- 
tries was  deeper  and  more  violet ;  whereas  that  from 
the  southern  regions  was  more  red.  This  author 
adds  that  the  color  was  obtained  by  beating  the  shell 
with  iron  tools,  and  that  the  purple  liquor  separated 
from  the  debris  of  the  animal  was  mixed  with  a  cer- 
tain proportion  of  honey. 

Dr.  Edward  Bancroft,  in  his  experimental  researches 
on  the  physical  properties  of  fast  colors,  remarks : 
"  The  purple  so  celebrated  among  the  ancients  ap- 
pears to  have  been  discovered  at  Tyr,  about  twelve 

centuries  before  the  Christian  era.    This  dye  was 

/ 


26 


MANUFACTURE  OF  COLORS. 


extracted  from  a  univalve  shell  (murex),  of  which 
there  were  two  species,  and  which  were  found  on  the 
shores  of  the  Mediterranean.  The  throat  of  the  ani- 
mal was  incised,  or  it  was  ground  whole,  and  the 
mixture  was  allowed  to  digest  for  several  days  with 
salt  and  water  in  leaden  vessels.  During  the  last 
period  of  the  Roman  Empire,  the  use  of  this  precious 
dye  was  restricted  to  a  few  dignitaries,  under  the 
heaviest  penalties. 

"  In  1683,  a  man,  who  was  making  a  living  in  Ire- 
land by  marking  linen  with  a  fine  crimson  color,  ex- 
tracted from  a  sea-shell,  found  out  after  some 
researches  on  the  coasts  of  Sommersetshire  and 
"Wales,  quantities  of  buccina,  which  gave  forth  a 
viscous  and  whitish  liquor  when  bled  near  the  head. 
Marks  made  with  this  liquor  would,  by  contact  with 
the  air,  become  of  a  soft  green  color  which,  by  expo- 
sure to  the  sun,  turned  by  degrees  to  a  fast  and  fine 
purple.  In  1769,  De  Jussieu  found  on  the  western 
coast  of  France,  a  species  of  buccinum  similar  to  the 
garden  snail ;  and  the  following  year,  de  Reaumur 
observed  that  on  the  coasts  of  Poitou  this  same  shell- 
fish was  very  abundant.  The  same  naturalist  had 
already  found,  in  1736,  on  the  shores  of  the  Mediter- 
ranean, the  purpura,  the  only  species  of  murex  which 
was  then  known.  All  these  shell-fish  furnish  a 
liquor,  which,  to  a  greater  or  less  extent,  possesses 
the  above-mentioned  properties." 

According  to  Pliny,  the  finest  purple  was  of  a  dark 
pink,  and  he  asserts  that  it  was  employed  for  impart- 
ing a  finishing  lustre  to  the  sandyx,  which  was  a 
compound  of  ochre  and  sandaraca  calcined  together, 
and  resembling  our  crimson. 

Blues, — This  color,  as  bright  as  ultramarine,  was 


lOTRODUCTION. 


27 


found  in  the  collection  of  Passalaqiia,  and  is  a  sort 
of  blue  ash,  vastly  superior  to  that  manufactured  at 
the  present  time.  The  latter,  indeed,  is  rapidly  acted 
upon  by  heat,  acids,  and  alkalies,  and  even  becomes 
green  by  age  ;  on  the  other  hand,  the  Egyptian  blue 
resists  the  action  of  all  these  agents,  and  retains  its 
brightness  after  thirty  centuries. 

A  blue  color,  taken  from  an  Egyptian  grave  at 
Thebes,  was  analyzed  by  Vauquelin.  This  blue  was 
quite  fusible.  Heated  with  the  blowpipe  upon  char- 
coal, and  with  the  addition  of  cream  tartar,  it  gave 
metallic  copper.  The  approximative  result  obtained 
by  this  chemist  was  : — 


Silica   10 

Lime   9 

Oxide  of  copper   15 

Oxide  of  iron   1 

Soda  and  potassa   4 


"  I  do  not  know,"  says  he,  "  whether  this  color  was 
prepared  by  the  wet  or  the  dry  way ;  but  it  is  certain 
that  the  constituent  parts  are  thoroughly  combined, 
since  concentrated  acids  remove  but  traces  of  copper 
and  lime,  and  nothing  at  all  at  a  second  treatment." 
Yauquelin  saw  a  similar  color  produced  in  the  bed 
of  a  copper  melting  furnace,  at  the  manufactory  of 
Romilly;  the  chemical  composition  and  the  tone  of 
the  blue  were  the  same.  This  Egyptian  blue  is  more 
than  thirty  centuries  old,  and  if  certain  parts  have 
been  slightly  altered,  it  is  only  at  the  surface.  Theo- 
phrastes  speaks  of  this  blue  color,  as  being  manufac- 
tured at  Alexandria,  and  having  been  discovered  by 
a  king.  "We  read  in  Yitruvius  that  Yestorius,  on  his 
return  to  Italy,  gave  its  composition.  It  was  prepared 
at  Pozzuoli,  by  triturating  together  copper  filings. 


28 


MANUFACTURE  OF  COLORS. 


sand,  and  natron,  and  forming  balls  which  were  after- 
wards heated  in  a  potter's  oven. 

Davy  succeeded  in  making  a  blue  color  similar  to 
that  of  Egypt,  by  strongly  heating  for  two  hours  a 
mixture  of — 

Pulverized  silicious  stone  20 

Carbonate  of  soda  15 

Copper  filings  3 

"The  blue  prepared  by  this  chemist,"  says  Julia 
de  Fontenelle,  "differs  from  that  analyzed  by 
Vauqueliu,  by  melting  at  a  lower  temperature  than 
the  Egyptian  blue ;  this  result  appears  to  be  due  to 
the  greater  proportion  of  carbonate  of  soda." 

"  The  blues  employed  by  the  ancients,"  says  Davy, 
"are  pale  or  dark,  according  as  the  proportion'  of 
carbonate  of  lime  is  greater  or  less  ;  but  when  the 
carbonate  of  lime  is  removed  by  acids,  they  have  the 
same  body  and  appearance,  that  is  to  say,  a  highly 
comminuted  blue  powder,  similar  to  the  finest  smalt 
and  ultramarine  blues.  This  powder  is  hard,  retains 
its  color  at  a  red  heat,  and  fuses  at  a  higher  temper- 
ature." Davy  ascertained  that  this  blue  color  was 
not  altered  by  the  acids ;  aqua  regia,  however,  after 
a  protracted  boiling  with  it,  becomes  yellow,  and 
shows  the  presence  of  copper.  A  certain  quantity 
of  this  color  was  kept  fused  for  half  an  hour  with 
double  its  weight  of  hydrated  potassa ;  the  mass  was 
of  a  greenish-blue,  and  after  treatment  with  hydro- 
chloric acid,  gave  a  proportion  of  silica  greater  than 
three-fifths  of  the  primitive  weight.  The  coloring 
matter  was  easily  dissolved  in  ammonia,  impart- 
ing to  the  latter  an  intense  blue  color,  from  which 
Davy  concludes  that  it  was  oxide  of  copper.  The 
residue  was  a  notable  quantity  of  alumina  with  a 
small  proportion  of  lime. 


INTRODUCTION". 


29 


The  small  amount  of  lime  found  in  that  color  did 
not  appear  to  Davy  sufficient  to  explain  its  fusibility  ; 
the  presence  of  an  alkali  was  therefore  suspected,  and 
after  the  proper  treatment,  a  residue  of  sulphate  of 
soda  was  obtained.  This  was  a  proof  that  the  color 
was  a  frit,  colored  by  oxide  of  copper.  According  to 
Davy,  there  appears  to  be  little  doubt  about  this  blue 
being  that  described  by  Theophrastes. 

Pliny  mentions  other  kinds  of  blues,  which  he  calls 
sands  (arence),  and  which  were  mined  in  Egypt, 
Scythia,  and  Cyprus.  Davy  believes  that  they  were 
various  preparations  of  lapislazuli,  and  the  blue 
carbonates  or  arseniates  of  copjDer. 

Pliny  and  Vitruvius  speak  of  the  Indian  blue,  the 
former  stating  that  it  was  combustible.  Evidently 
it  was  a  kind  of  indigo. 

Davy  examined  several  blues  from  fresco  paintings 
in  the  ruins  of  the  monument  of  Caius  Cestius ;  one 
was  of  a  dark  indigo  color,  and  yielded  a  small  pro- 
portion of  carbonate  of  copper  ;  but  the  basis  of  the 
color  was  the  above  described  frit.  The  blues  of  the 
Aldobrandini  Wedding,  from  their  resistance  to  the 
heat  and  acids,  are  believed  by  Davy  to  be  com- 
pounds of  Alexandria  blue. 

In  diggings  made  in  1814,  at  Pompeii,  and  in  the 
presence  of  Davy,  a  small  pot  was  found,  holding  a 
pale  blue  color.  It  was  nothing  else  than  a  mixture 
of  lime  and  Alexandria  frit. 

M.  Girardin,  Professor  of  Chemistry  at  Lille,  has 
analyzed  a  substance  of  a  light  blue  color,  found  in 
a  Gallo-Poman  city  of  the  department  of  Seine-Infe- 
rieure.  After  treatment  with  weak  hydrochloric 
acid,  which  removed  a  certain  proportion  of  carbonate 
of  lime,  the  residue  was  of  a  very  fine  azure-blue  color. 
The  composition  of  the  substance  was  as  follows : — 


30 


MANUFACTURE  OF  COLORS. 


Silica  

Alumina  

Lime,  with  traces  of  magnesia  and  iron  . 


49.4 
6.4 
19.5 
15.5 
9.3 


Soda 

Oxide  of  copper 


100.1 


After  having  mentioned  the  analyses  made  by 
Chaptal  and  Davy,  Mr.  Girardin  passes  to  the  fol- 
lowing extract  from  the  Histoire  de  la  Chimie.hj 
Hoefer :  "  The  manufacture  of  blue  was  invented  at 
Alexandria,  and  JS'estorius  for  a  long  time  prepared 
it  at  Pozzuoli.  Sand  and  natron  (carbonate  of  soda) 
are  ground  together  as  fine  as  flour,  and  then  mixed 
with  copper  filings  and  a  little  water,  in  order  to 
make  a  paste.  Balls  are  made  with  this  paste,  and 
are  allowed  to  dry ;  lastly,  they  are  put  into  pots,  and 
heated  in  a  furnace  in  order  that  they  may  fuse  and 
produce  a  blue  color."    Mr.  Grirardin  then  adds  : — 

"  This  color,  which  is  remarkable  for  its  beauty 
and  durability,  could  actually  be  prepared  by  calcin- 
ing for  two  hours  in  a  furnace  a  mixture  of — 

Silicious  sand  60  parts 

Soda  ash  45  " 

Copper  filings  10  " 

Oreens, — Merimee  says  that  he  saw  no  bright 
greens  in  the  above-mentioned  Egyptian  collection. 
All  of  them  being  olive-green,  he  believed  at  first 
that  they  were  made  of  a  kind  of  chlorite,  inferior  in 
brightness  to  Yerona  earth,  still  in  use  by  our  paint- 
ers. But  he  soon  found  out  by  analysis  that  copper 
was  the  coloring  element. 

A  fragment,  detached  from  the  ceiling  of  the  baths 
of  Livia,  was  of  a  dark  sea-green,  like  the  ground- 
work.   Davy  ascertained  that  the  coloring  substance 


INTRODUCTIOlSr. 


31 


was  soluble  with  effervescence  in  acids,  and  when 
precipitated  and  redissolved  in  ammonia,  it  imparted 
the  blue  color  due  to  the  oxide  of  copper.  "  There 
are,"  says  Davy,  "  different  tones  of  green  employed 
in  the  baths  of  Titus,  and  also  upon  the  fragments 
found  in  the  monument  of  Caius  Cestius."  In  the 
vases  holding  mixed  colors,  already  mentioned,  Davy 
found  three  different  varieties  of  green  ;  one,  with  an 
olive  shade,  was  Verona  earth ;  the  other  was  a  pale 
grass-green,  and  had  the  appearance  of  being  carbon- 
ate of  copper  mixed  with  chalk ;  the  third  was  sea- 
green,  and  was  a  combination  of  copper  mixed  with 
a  blue  copper  frit. 

All  of  the  greens  examined  by  Davy,  in  the  baths 
of  Titus,  were  copper  compounds.  The  green  of  a 
grapevine  was  so  bright  that  it  was  suspected  to 
contain  arsenic,  like  Scheele's  green,  but  analysis 
demonstrated  that  it  was  pure  carbonate  of  copper. 

Yitruvius  speaks  of  chrysocoUa  as  a  substance 
found  naturally  in  copper  mines,  and  Pliny  mentions 
artificial  chrysocolla,  made  with  a  clay  found  in 
proximity  to  metallic  veins.  This  clay  was  probably 
impregnated  with  copper,  and  Davy  believes  that  the 
natural  chrysocolla  was  a  carbonate  of  copper, 
whereas  the  artificial  chrysocolla  was  clay  impreg- 
nated with  sulphate  of  copper,  and  rendered  green 
by  some  yellow  substance. 

Davy  thinks  that  the  name  of  chrysocolla  is  de- 
rived from  the  green  powder  employed  by  gold- 
smiths, having  carbonate  of  copper  as  a  component 
part. 

Among  the  substances  found  in  the  baths  of  Titus, 
some  were  of  a  grass-green  color.  Davy  at  first 
thought  that  they  were  specimens  of  natural  chryso- 


32 


MANUFACTURE  OF  COLORS. 


coUa,  but  he  afterwards  ascertained  that  they  were 
carbonate  of  copper.  There  were  also  round  nodules 
of  the  i*ed  sub-oxide  of  copper,  which,  it  is  surmised, 
were  due  to  nails  or  small  plates  of  copper  converted 
into  oxide  and  carbonate,  by  the  action  of  the  air 
during  several  centuries. 

According  to  Theophrastes,  the  ancients  were  well 
acquainted  with  verdigris.  Yitruvius  speaks  of  it 
as  a  color,  and  it  is  likely  that  many  ancient  greens 
which  are  now  carbonates,  were  primitively  employed 
in  the  form  of  acetates. 

The  ancients  had  glass  of  a  very  handsome  dark 
green  color.  Davy  ascertained  that  they  were  col- 
ored by  the  oxide  of  copper  ;  but  it  does  not  appear 
that  such  glasses  were  powdered  and  then  used  as 
paints. 

All  the  greens  of  the  Aldobrandini  "Wedding  were 
shown  by  Davy  to  be  derived  from  copper. 

In  March,  1809,  Chaptal  reported  to  the  Academy 
of  Science  the  results  of  his  examination  of  seven 
samples  of  paints  found  at  Pompeii,  in  a  color  store. 

The  first  of  these  colors  was  a  natural  product,  a 
greenish  and  soapy  clay,  such  as  is  found  in  several 
countries.  This  color  appeared  to  Chaptal  as  being 
analogous  to  Verona  earth. 

Number  two  was  a  fine  yellow  ochre,  freed  by 
washing  from  all  the  foreign  substances  impairing 
either  its  purity  or  its  fineness.  Since  this  substance 
becomes  red  by  calcination  at  a  moderate  heat,  its 
yellow  color,  which  was  fully  preserved,  seems  to 
Chaptal  an  additional  proof  that  the  ashes  which 
buried  Pompeii  were  but  moderately  hot. 

Number  three  was  a  brown-red,  similar  to  that 
employed  at  the  present  time  for  coarse  paintings 


IXTRODUCTIOlsr. 


33 


upon  barrels  and  doors,  windows,  etc.  This  color  is 
produced  by  the  calcination  of  yellow  ochre. 

ISTumber  four  was  a  very  light,  white,  and  close- 
grained  pumice-stone. 

The  three  other  samples  were  compound  colors, 
which  Chaptal  was  obliged  to  analyze,  in  order  to 
arrive  at  their  constituent  parts. 

Number  five  was  an  intense  blue,  in  small  frag- 
ments of  equal  size  and  shape.  The  exterior  was 
lighter  than  the  inside,  the  color  of  which  was  deeper 
and  brighter  than  the  finest  blue  ashes. 

This  color  produces  but  a  slight  effervescence  with 
hydrochloric,  nitric,  and  sulphuric  acids ;  it  even 
becomes  brighter,  and  chlorine  has  no  effect  upon  it. 
There  is,  therefore,  no  similarity,  according  to  Chap- 
tal, to  ultramarine  blue,  since  the  latter  is  destroyed 
by  the  four  above-named  reagents,  as  has  been  ob- 
served by  Clement  and  Desormes. 

Ammonia  has  no  action  upon  it.  Heated  with  a 
blowpipe,  it  darkens  and  forms  a  reddish-brown  frit. 
It  colors  borax  a  greenish-blue.  Treated  with  po- 
tassa  upon  a  platinum  support,  it  produces  a  greenish 
frit,  which  becomes  brown  and  then  copper-colored. 
This  frit  is  partly  soluble  in  water;  hydrochloric 
acid,  poured  into  the  solution,  produces  a  gelatinous 
precipitate.  Oxalate  of  ammonia  gives  another  pre- 
cipitate with  the  separated  liquor. 

Nitric  acid  dissolves  with  effervescence  the  residue 
unacted  upon  by  the  alkali.  The  solution  is  green,  and 
gives  with  ammonia  a  precipitate  which  is  redissolved 
by  an  excess  of  the  reagent ;  the  liquor  is  then  blue. 

"This  color,"  says  Chaptal,  "appears,  therefore,  as 
a  compound  of  oxide  of  copper,  lime,  and  alumina;  it 
contains  the  elements  of  blue  ashes,  but  its  chemical 
3 


34 


MANUFACTURE  OF  COLORS. 


properties  are  different.  It  appears  to  be  not  a  pre- 
cipitate but  a  frit,  that  is  to  say,  the  beginning  of  a 
vitrification." 

It  appears  that  the  process  by  which  the  ancients 
obtained  that  color,  is  lost  to  us.  All  that  we  know 
is  that  such  a  blue  was  employed  centuries  before 
Pompeii  was  buried  in  ashes.  "Descotil,"  adds 
Chaptal,  "  has  observed  a  bright  blue  with  a  vitreous 
lustre  upon  the  hieroglyphic  paintings  on  an  Egyp- 
tian monument,  and  he  ascertained  that  the  color  was 
due  to  copper. 

"  From  its  component  parts,  that  color  may  be  com- 
pared with  our  modern  blue  ashes ;  but  in  regard  to 
usefulness,  we  may  substitute  for  it  the  ultramarine 
and  azure  blues." 

Number  six  is  a  light  blue  sand,  mixed  with  a  few 
whitish  granules.  Chemical  tests  demonstrated  the 
presence  of  the  same  substances  found  in  the  preced- 
ing number.  "We  may,"  says  Chaptal,  "consider  it 
as  a  similar  compound  with  greater  proportions  of 
silica  and  alumina." 

The  color  of  number  seven  is  a  handsome  pink. 
The  material  is  smooth  and  is  reduced  to  an  impalpa- 
ble powder  between  the  fingers,  coloring  the  skin  a 
pretty  carnation  pink.  By  heat  this  color  blackens, 
and  lastly  turns  white,  without  any  sensible  smell  of 
ammonia.  This  color  is  soluble  in  hydrochloric  acid 
with  a  slight  efiervescence,  and  ammonia  produces  in 
the  solution  a  flocculent  precipitate  entirely  soluble 
in  potassa.  An  infusion  of  gall-nuts,  and  the  hydro- 
sulphate  of  ammonia  fail  to  show  the  presence  of 
any  metal. 

We  may,  according  to  Chaptal,  consider  this  pink 
color  as  a  true  lake,  the  coloring  principle  of  which 


INTRODUCTION. 


35 


is  absorbed  by  alumina.  Its  properties,  shade,  and 
the  nature  of  its  coloring  principle  render  it  almost 
entirely  analogous  with  madder  lake.  The  preserva- 
tion of  this  lake  for  nineteen  centuries,  without 
being  scarcely  at  all  altered,  is  a  wonderful  phenome- 
non for  chemists. 

Such,  says  Chaptal,  is  the  nature  of  the  seven  colors 
which  were  submitted  to  him,  and  they  seem  to  have 
been  especially  intended  for  painting.  Nevertheless, 
he  observes  that  if  we  examine  the  varnish  or  glaze 
of  Roman  potteries,  the  debris  of  which  are  so  plen- 
tiful wherever  the  armies  of  Rome  established  them- 
selves, we  can  easily  believe  that  most  of  these  color- 
ing earths  could  also  have  been  employed  for  glazing 
those  potteries. 

The  azure  blue,  the  red  and  yellow  ochres,  and  the 
blacks,  are  colors  which,  according  to  Davy,  do  not 
seem  to  have  been  altered  at  all  in  the  fresco  paint- 
ings. The  vermilion  is  darker  than  the  cinnabar  of 
Holland,  and  the  lustre  of  the  red  lead  is  inferior  to 
that  sold  at  the  present  time.  The  greens  are  gene- 
rally dull. 

"The  principle  of  the  composition  of  the  Alexan- 
dria frit,"  adds  Davy,  "is perfect,  i.  e.,  to  incorporate 
the  color  in  a  composition  resembling  stone,  in  order 
to  prevent  the  disengagement  of  any  elastic  fluid,  or 
the  decomposing  action  of  the  atmosphere.  It  is  a 
kind  of  artificial  lapis-lazuli,  the  coloring  substance 
of  which  is  thoroughly  combined  with  a  very  hard 
silicious  stone. 

"  It  is  likely  that  other  colored  frits  could  be  made, 
and  it  would  be  worth  while  to  try  whether  a  fine 
purple,  from  gold  oxide,  could  not  be  rendered  use- 
ful for  painting,  by  incorporating  it  with  a  glass. 


36 


MANUFACTUKE  OF  COLORS. 


When  frits  cannot  be  employed,  the  experience  of 
seventeen  centuries  demonstrates  that  the  best  colors 
are  metallic  combinations,  insoluble  in  water,  and 
saturated  with  oxygen  or  some  acid  substance.  In 
red  ochres,  the  oxide  of  iron  is  saturated  with  oxy- 
gen ;  in  the  yellow  ochres,  the  metal  is  combined  with 
oxygen,  and  sometimes  with  carbonic  acid.  These 
colors  have  remained  unchanged.  The  carbonates  of 
copper,  which  contain  an  oxide  and  an  acid,  have  been 
but  slightly  altered." 

Several  parts  of  the  figures  and  ornaments  on  the 
outside  of  the  baths  of  Titus,  present  only  traces  of 
ochreous  colors,  and  Davy  thought  it  likely  that 
vegetable,  such  as  indigo,  or  animal  colors,  or  differ- 
ent colored  clays,  had  been  employed. 

To  sum  up,  the  most  minute  investigations,  and  the 
most  thorough  examinations  of  ancient  monuments, 
have  revealed  to  chemists  none  others  than  white, 
black,  yellow,  brown,  red,  blue,  and  green  colors. 


/ 


ORIGIN,  ETC.,  OF  COLORS. 


37 


CHAPTEE  1. 

ORIGm,  DEFINITION,  AND  CLASSIFICATION  OF 
COLORS. 

SECTION  L 

ORIGIN  OP  COLORS. 

The  decomposition  of  a  ray  of  light  furnishes  seven 
distinct  colors — violet^  indigo^  hlue^  green,  yellow, 
oran/e,  and  red,  which  are  generally  called  the  normal 
colors.  We  may,  however,  say  that  hlue,  yellow,  and 
red  are  really  the  only  primary  colors,  since  they  are 
sufficient  to  reproduce  all  the  others.  White  is  the 
reunion  of  the  seven  colors,  or  the  light  of  a  solar 
ray  ;  and  hlach  is  the  entire  absence  of  this  light. 

The  whites  employed  in  painting  are  not  a  mix- 
ture of  all  the  colors  ;  they  are  natural  or  chemical 
compounds,  which  reflect  light  without  decomposing 
it  as  other  pigments  do.  The  blacks  absorb  and  pre- 
vent the  luminous  intensity  of  the  other  colors. 

In  general,  the  pure  color  of  a  substance  is  that 
of  the  color  of  the  prismatic  spectrum  which  it 
reflects  to  our  eyes.  A  blue  substance  reflects  blue 
rays  only,  and  absorbs  all  others.  A  yellow  body 
reflects  but  yellow  rays  ;  a  red  body  reflects  but  red 
rays,  etc.  A  white  substance  reflects  all  the  rays  of 
the  spectrum,  and  it  is  their  confused  reunion  with  the 
same  degree  of  intensity  that  appears  white  to  our 
eyes.  A  black  substance  absorbs  all  the  colors  of 
the  spectrum  and  reflects  none. 


38 


MANUFACTURE  OF  COLORS. 


The  combination  of  the  seven  colors  of  the  prisma- 
tic spectrum  produces  hues  which  can  be  varied  ad 
infinHum^  by  the  proper  mixture  of  pigments.  These 
hues  are  often  called  secondary  colors  in  contradis- 
tinction with  the  normal  colors  of  the  spectrum. 

The  coloring  substances  employed  for  painting  are 
either  natural  or  artificial ;  but,  as  they  are  generally 
too  light,  they  are  mixed  with  white  lead,  which  im- 
parts to  them  body  and  durability. 

The  admixture  of  white  with  these  colors  renders 
them  more  luminous  by  diminishing  the  intensity  of 
their  pure  color.  On  the  other  hand,  black  renders 
the  other  colors  less  luminous  by  a  kind  of  absorp- 
tion, without  sensibly  altering  their  specific  character. 

The  effects  resulting  from  the  mixture  of  colors 
with  blacks  or  whites,  are  totally  different  from  those 
due  to  the  mixture  of  colors  together.  This  should 
be  remembered  by  the  painter,  for  it  is  almost  im- 
possible to  obtain  bright  hues  with  an  admixture  of 
black.  It  has  even  been  observed  that  the  grays  ob- 
tained by  the  combination  of  black  and  white,  are 
not  so  fine  and  advantageous  as  the  gray  shades 
resulting  from  the  combination  of  the  primary  colors. 

We  shall  not,  in  this  place,  tarry  any  longer  on  the 
innumerable  phenomena  of  the  art  of  coloring,  since 
we  shall  return  to  them  when  speaking  of  the  manu- 
facture qfcolo7^s,  which  requires  a  thorough  knowledge 
of  the  coloring  substances,  whether  natural  or  artifi- 
cial, and  of  the  manner  of  using  them.  Without 
insisting  more  than  is  necessary  upon  the  systematic 
division  of  normal  or  secondary  colors,  whether  nat- 
ural or  artificial,  we  shall  proceed  to  fully  examine 
the  various  processes  for  extracting  and  purifying, 
or  manufacturing,  all  the   colors  or  pigments  for 


ORIGMN,  ETC.,  OF  COLORS. 


39 


painting.  These  colors  are :  the  whites.  Hues,  yel- 
lows^ blacks,  reds,  and  greens  ;  and  in  order  to  facili- 
tate our  researches,  we  shall  follow  the  above  order, 
and  put  the  oranges  and  violets  after  the  reds,  and  the 
browns  with  the  blacks.  As  for  the  combinations 
necessary  to  arrive  at  a  given  hue  or  tone,  we  shall 
state  the  general  principles,  necessary  in  the  majority 
of  cases,  and  sufficient  to  obtain  an  infinite  variety  of 
hues  and  tones. 

SECTION  11. 

DETERMINATION  AND  DEFINITION  OF  COLORS. 

The  study  of  colors,  in  regard  to  their  nature  and 
their  reactions  upon  each  other,  is  highly  interesting. 
"We  are  indebted  to  M.  Chevreul  for  a  new  method 
and  nomenclature,  which,  sooner  or  later,  will  prevail 
in  the  arts,  and  which  is  based  upon  the  chromatic 
circles  invented  by  this  learned  chemist. 

In  this  method,  all  the  colors  are  derived  from  in- 
variable types  or  standards,  disposed  in  a  certain 
order  comprising  the  hemispherical  chromatic  con- 
struction. 

We  know  that  every  color,  whatever  be  its  nature, 
is  either  simple  or  compound,  luminous  or  sombre, 
that  is,  pure  or  broken.  Here  is  the  mode,  by  means 
of  the  hemispherical  chromatic  construction,  of  arri- 
ving at  the  comparison  and  determination  of  colors 
or  of  their  modifications  : — 

Let  us  suppose  a  circle,  divided  into  three  equal 
parts,  by  three  radii ;  at  the  end  of  any  one  of  these 
radii  we  write  the  word  red  ;  at  the  extremity  of  the 
other  radius  on  the  right,  we  write  yelloiv  ;  and  at  the 
end  of  the  other  radius  blue.    "We  then  divide  each  ^ 


40 


MANUFACTURE  OF  COLORS. 


of  these  intervals  by  other  radii,  termed  orange, 
between  the  red  and  the  yellow ;  gree7i  between  the 
yellow  and  the  blue,  and  violet  between  the  red  and 
the  blue.  Still  subdividing  each  of  these  ten  divi- 
sions, we  have  the  orange-red,  the  orange-yellow,  the 
green-yellow,  the  green-hlue,  the  violet-hlue,  and  the 
violet-red.  We  then  divide  each  interval  into  six 
equal  parts,  and  fill  the  first  one,  from  the  radius 
"  red,"  for  instance,  with  red,  and  the  other  five  with 
proper  mixtures  of  red  and  yellow,  in  such  a  manner 
that  the  change  in  hue  is  gradual.  These  five  spaces 
are  called  :  first  red,  second  red,  third  red,  fourth  red, 
and  fifth  red.  "We  operate  in  the  same  manner  with 
all  the  other  colors. 

The  primitive  circle  is,  therefore,  subdivided  into 
seventy-two  equal  angular  parts,  each  of  them  hav- 
ing a  name  which  does  not  change.  We  understand 
that  any  simple  or  compound  color,  but  pure,  i.  e., 
without  admixture  of  gray,  must  correspond  with  one 
of  the  seventy -two  primitive  types  or  standards,  or 
be  found  between  two  consecutive  types.  But  the 
latter  case  seldom  happens,  and  it  is  always  possible 
to  interpolate  by  one-half,  one-third,  one-quarter,  etc. 

The  broken  colors  are  determined  in  the  same 
manner,  by  means  of  types  or  standards.  Indeed,  let 
us  suppose  that  a  quadrant  is  placed  perpendicular  to 
the  plan  of  each  color  of  the  first  circle,  and  that  the 
quadrant  is  divided  into  ten  equal  parts.  Each  sec- 
tion will  receive  the  color  modified  in  tone,  the  first 
by  of  black,  the  second  by  ^\  of  black,  and  so  on, 
until  the  tenth  contains      that  is  to  say,  pure  black. 

In  practice,  the  hemispherical  chromatic  construc- 
tion is  reduced  to  ten  chromatic  circles.  The  first 
contains  the  pure  colors ;  the  second  the  chromatic 


% 


OKIGIN,  ETC.,  OF  COLORS. 


41 


gamuts,  or  scales,  broken  with  of  black;  the  third 
the  colors  broken  with  -^^  of  black,  and  so  on. 

All  the  pure  colors  are  not  equally  intense,  and  their 
coloring  power  is  modified  by  white.  Mr.  Chevreul 
indicates  the  depth  of  the  color  by  the  distance  from 
that  color  to  the  centre  of  the  circle,  in  the  following 
manner :  Any  one  of  the  radii  which  separate  the 
seventy-two  hues,  is  divided  into  twenty-two  equal 
parts  by  twenty-one  equidistant  points,  through 
which  the  same  number  of  circumferences  are  made 
to  pass.  Therefore,  every  angular  section  of  the 
seventy-two  hues  is  divided  into  twenty-two  spaces. 
In  order  to  fill  each  of  these  divisions,  we  suppose 
that  all  the  hues  are  gradually  tinted  or  toned  in 
such  a  manner  that,  the  centre  being  white,  the  first 
space  is  slightly  tinted,  the  second  a  little  more,  the 
third  still  more,  and  so  on  until  the  twentieth,  which 
is  near  the  black.  The  first  division,  or  white,  is 
marked  0 ;  the  last  is  black,  and  is  marked  21.  The 
whole  graduation  is  a  gamut,  or  scale,  of  which  there 
are  seventy-two  in  the  whole  circle.  The  parts  of 
this  gamut  are  called  tones.  The  first  tone  is  that  com- 
prised between  the  first  and  second  circumferences  ; 
the  second  tone  is  that  between  the  second  and  third 
circumferences,  and  so  on. 

The  color  of  many  chemical  products  and  coloring 
substances  is  often  an  indication  of  their  purity,  and 
it  is  therefore  necessary  to  define  well  their  colora- 
tion, and  to  fix  it  between  stated  limits  so  that  but 
slight  variations  should  be  allowed. 

We  shall  add  that  a  manufacturer  of  Paris,  Mr. 
Digeon,  has  undertaken  to  provide  the  public  by 
chromo-engravings,  with  the  chromatic  circles  of  Mr. 
Chevreul,  and  that  he  has  succeeded  perfectly  well  in 


42 


MANUFACTURE  OF  COLORS. 


this  work,  which  requires  both  skill  and  patience. 
The  series  of  these  circles  is  cheap  enough,  and  should 
be  found  in  the  shop  of  every  painter  or  manufacturer 
of  colors. 

Since  Mr.  Chevreul  has  published  his  fundamental 
ideas  upon  the  definition  and  the  manner  of  naming 
colors,  he  has  communicated  to  the  Academy  of 
Sciences  several  new  details,  which  better  express 
their  nature  and  applications. 

"  The  arrangement,''  says  he,  "  described  in  my 
work  on  the  Laws  of  the  Simultaneous  Contrast  of 
Colors,  under  the  name  of  the  hemispherical  chromatic 
construction,  comprises  upon  a  circular  plane  72  dis- 
tinct colors,  which  I  call  a  ][>ure  gamut.  Each  gamut 
comprises  20  tones  of  the  same  color,  the  intensity  of 
which  increases  from  the  centre,  which  is  white,  to 
the  circumference,  outside  of  which  the  normal  black 
is  supposed  to  be.  The  first  10  tones,  at  least,  of 
each  of  the  72  gamuts  of  the  circle,  contain  but  pri- 
mary colors,  such  as  red,  blue,  and  yellow,  or  Unary 
colors,  so  called  because  they  are  compounds  of  two 
primaries.  These  first  10  tones,  at  least,  being  with- 
out black,  are  oaWed  pure  tojies,  and  are  characteristic 
of  the  chromatic  circle  of  72  gamuts,  just  mentioned, 
and  which  I  call  No.  1,  as  will  be  explained  farther 
on.  12  gamuts  have  the  following  names  :  red, 
orange-red,  orange,  orange-yellow,  yellow,  yellow-green, 
green,  green-blue,  blue,  hlue-violet,  violet,  violet-red;  and 
60  gamuts  are  by  series  of  five,  between  two  of  the 
above-mentioned  gamuts.  The  series  or  interpolated 
gamuts  are  numbered  1,  2,  3,  4,  5,  to  which  is  added 
the  name  of  the  preceding  gamut,  in  the  order  men- 
tioned.   For  instance,  the  gamuts  comprised  between 


ORIGIN,  ETC.,  OF  COLORS. 


43 


the  red  and  orange-red  are,  1st  red,  2d  red,  3d  red, 
4th  red,  and  5th  red,  and  so  on. 

"  But  are  these  1440  hues  and  tones,  belonging  to 
72  gamuts,  sufficient  to  denominate  all  colors?  Evi- 
dently not.  We  now  have  to  demonstrate  how  the 
quadrant  of  the  hemispherical  chromatic  construction 
completes  the  modification  of  all  the  tones  of  the 
chromatic  circle  by  the  addition  of  black.  The  colors 
are  rendered  gray,  or  hroken^  not  only  for  the  first  10 
tones,  at  least,  without  black,  belonging  to  the  72 
gamuts,  or  scales,  of  the  circular  plan,  but  also  for 
the  other  tones  already  broken. 

"  The  quadrant  being  supposed  mobile  upon  its 
axis,  and  perpendicular  to  the  centre  of  the  circular 
plan,  describes  during  its  rotation,  a  hemisphere, 
which  comprises  all  the  modifications  possible  by  the 
mixture  with  black  of  the  20  tones  of  each  of  the  72 
gamuts.  In  order  to  understand,  let  us  make  the 
quadrant  coincident  with  one  of  the  gamuts  of  the 
circular  plan,  the  red  for  instance.  The  quadrant  is 
divided  by  ten  equidistant  radii,  including  the  axis, 
and  the  latter  is  also  divided  into  20  equal  parts  for 
the  20  tones  of  graduated  mixtures  of  white  and 
black  corresponding  to  the  20  tones  of  the  red  gamut 
of  the  circular  plan.  Each  of  the  spaces  formed  by 
the  9  other  radii  of  the  quadrant,  comprises  1  gamut 
of  20  tones  of  red  shaded  with  black,  the  latter  being 
increased  uniformly  from  the  red  gamut  shaded  with 
black  of  the  circular  plan  to  the  axial  gamut  of  nor- 
mal gray.  We  shall  then  have  9  gamuts  of  broken 
red  thus  made  :  1st  red,  +  i  o  black  ;  2d  red,  + 
y\  black  ;  3d  red,  +  to  black  ;  4th  red,  y%  + 
black ;  5th  red,  -^^  +  -f-^  black  ;  6th  red,  y%  + 
black ;  7th  red,      +  to  black  ;  8th  red,  y\  +     black  ; 


44 


MANUFACTURE  OF  COLORS. 


9th  red,  +  t\  black.  What  is  said  about  the  red 
can  be  applied  to  the  71  other  gamuts  of  the  circular 
plan. 

"  Thus,  for  each  gamut  of  the  circular  plan,  there 
are  9  gamuts  of  the  color,  broken  in  all  its  tones  by 
quantities  of  black,  increasing  regularly  (to  the  eye) 
from  the  circular  plan  to  the  axis  of  the  quadrant. 
The  hemispherical  chromatic  construction  therefore 
comprises — 

"I.  72  gamuts,  said  to  he  pure,  because  the  first  10 
tones,  at  least,  of  each  of  them  contain  no  black. 

^'11.  72  gamuts,  said  to  be  hroJcen,  because  their 
first  10  tones,  at  least,  contain  black. 

"  These  72  broken  gamuts  comprise  12,960  tones. 

"  III.  Lastly,  by  adding  the  20  tones  of  the  gradu- 
ated normal  black,  we  have — 

72  gamuts,  each  with  20  tones  =  1,440  tones 

648  gamuts  broken  in  the  20  tones      =  12,960  " 
1  gamut  of  normal  grays  =       20  " 

14,420  " 

"  Let  US  suppose  that  the  color  of  any  substance 
corresponds  to  11  tones  of  the  gamut  3  red  broken  by 
y\,  we  shall  write :  3d  red,  11  tones,  y\. 

"  ^fow,  we  will  understand  that  if  the  72  gamuts 
broken  by  -^^  of  black  are  put  in  a  circle,  and  the  72 
gamuts  broken  by  -^^  of  black  are  put  in  another 
circle,  and  so  on,  we  shall  have  9  circles  of  broken 
colors.  By  adding  to  them  the  first  circle  contain- 
ing the  first  10  pure  tones,  at  least,  we  shall  have  10 
chromatic  circles,  and  the  broken  circles  will  be  num- 
bered ^fos.  2,  3,  4,  5,  6,  7,  8,  9,  and  10. 

"  Up  to  the  present  time,  the  manufacture  of  the 
Gobelins  has  produced  but  1440  tones  of  the  first 


ORIGIN",  ETC.,  OF  COLORS. 


45 


chromatic  circle,  and  72  tenth  tones  of  the  648  broken 
gamuts. 

"  On  the  other  hand,  a  skilful  artist,  Mr.  Digeon, 
has  produced,  cheap  enough  for  the  trade,  colored 
plates  comprising  the  10  tones  of  the  10  chromatic 
circles.  He  has  also,  by  means  of  a  prism  of  bisul- 
phide of  carbon,  and  conformably  to  the  rays  of 
Fraunhofer,  reproduced  the  position  of  15  standard 
colors  corresponding  to  15  standard  colors  of  the  first 
chromatic  circle.  In  this  manner  it  will  always  be 
possible  to  find  these  types  again,  and  to  interpolate 
afterwards  the  other  colors  of  that  first  circle. 

"  Lastly,  Mr.  Digeon  has  made  three  plates  which 
show  to  the  eyes — 

"  I.  How  a  color,  blue  for  instance,  which  between 
the  limits  of  white,  0  color,  up  to  black,  representing 
21  tones,  may  give  20  distinct  tones  by  one  of  my 
established  rules. 

"  II.  How  a  color  and  its  hues,  by  going  from  red 
to  yellow,  from  yellow  to  blue,  and  from  blue  to  red, 
may,  according  to  the  same  rule,  give  72  gamuts  of 
distinct  colors. 

"  I  set  great  stress  on  what  I  have  just  said  {i,  e., 
the  artifice  by  which  I  succeed  in  reducing  an  inde- 
finite property,  such  as  a  given  color,  to  well-defined 
types  or  standards  constituting  the  20  tones  of  that 
color,  and  the  color  in  general  considered  as  having 
its  hues  in  definite  types  of  72  gamuts),  because  this 
method  may  be  applied  to  the  study  of  properties  or 
relative  properties  which  belong  to  various  sciences, 
the  object  of  which  is  the  study  and  classification  of 
bodies." 


46 


MANUFACTURE  OF  COLORS. 


SECTION  III. 


PHYSICAL  EFFECTS  OF  COLORS. 

Colors  of  the  rays  of  the  solar  spectrum, 

1.  Red.  5.  Blue. 

2.  Orange.  6.  Indigo. 


3.  Yellow. 

4.  Green. 


t.  Yiolet. 


The  reunion  of  the  rays  Red,  Yellow,  and  Blue 

"  "  Yellow  and  Red 

"  "  Yellow  and  Blue 

"  "  Red  and  Blue 


White. 
Orange. 
Green. 
Yiolet. 


Since  Yellow,  Red,  and  Blue  are  sufficient  to 
produce  all  the  other  colors,  they  have  been  called 
the  primary  colors. 

The  reflected  colors  which,  being  added  to  those 
absorbed,  reproduce  the  white,  are  called  compZemm^- 
ary  colors. 


Absorbed  Colors. 

Green  {Blue  and  Yellow) 

Yiolet  {Red  and  Blue) 

Orange  {Red  and  Yellow) 

Red 

Yellow 

Blue 


Corresponding  Complementary 
Colors. 

Red 

Yellow 

Blue 

Green  {Blue  and  Yellow) 
Yiolet  {Red  and  Blue) 
Orange  {Yellow  and  Red) 


.  Mr.  Chevreiil  calls  contrast  of  tone,  the  modification 
experienced  by  two  colors  of  the  same  nature,  but  of 
different  tones,  when  they  are  contiguous  one  to  the 
other. 

Example, — When  two  bands  of  the  same  color,  but 
of  different  intensity,  are  placed  parallel  and  conti- 
guous to  each  other,  they  are  modified  in  their  tones, 
which  are  no  longer  the  same  as  when  they  were 
viewed  separately,  or  at  a  certain  distance  from  each 


ORIGIN,  ETC.,  OF  COLOES, 


47 


other.  The  general  observed  phenomenon  is  this : 
the  color  of  the  two  bands  is  entirely  changed  at  the 
line  of  contact,  and  that  band  with  the  less  depth  of 
tone  appears  still  lighter,  but  not  uniformly  so.  The 
portions  nearest  the  line  of  contact  are  the  lightest, 
and  the  tone  goes  on  increasing  in  depth  up  to  a  cer- 
tain place,  where  the  band  retains  its  natural  color. 
On  the  other  hand,  the  darker  band  is  modified  in 
another  manner  :  the  portions  nearest  the  line  of  con- 
tact are  darkest,  and  the  tone  goes  on  decreasing  in 
depth  up  to  a  certain  place,  where  the  band  reac- 
quires its  natural  color. 

"When  two  stripes  of  different  colors,  but  sensibly 
equal  in  tone,  are  parallel,  and  in  contiguity,  their 
colors  produce  upon  the  eye  an  effect  different  from 
that  felt  if  they  are  seen  separately,  or  at  a  certain 
distance  from  each  other.  Each  one  absorbs  a  cer- 
tain number  of  rays,  and  reflects  the  complementary 
ones,  which,  reacting  one  upon  the  other,  modify  the 
examined  color.  This  optical  phenomenon  is  called 
by  Mr.  Chevreul  contrast  of  colors. 


Examples : — 

Juxtaposited 

Corresponding  Com- 

Modification by  Contrast. 

Colors. 

plementary  Colors. 

Orange. 

Blue 

=  Reddish-Orange. 

Green. 

Red 

=  Bluish-Green. 

Orange. 

Blue 

=  Orange  changing  to  Yellow. 

Indigo. 

Orange-Yellow 

=  Indigo  changing  to  Blue. 

Green. 

Red 

=  Green  changing  to  Orange- Yellow. 

Indigo. 

Orange-Yellow 

=  Indigo  changing  to  Red. 

Green. 

Red 

=  Green  changing  to  Yellow. 

Yiolet. 

Yellow  changing 

to  Green 

=  Yiolet  changing  to  Red. 

Red. 

Green 

=  Red  changing  to  Orange. 

Blue. 

Orange 

=  Blue  changing  to  Green. 

48 


MANUFACTURE  OF  COLORS. 


Mr.  Chevreul,  in  his  celebrated  work  on  the  con- 
trast of  colors,  has  fully  explained  the  meaning  of 
simultaneous  contrast  successive  contrast^  and  mixed 
contrast  We  advise  persons  desirous  of  gaining 
further  information  on  this  subject,  to  consult  that 
work. 

SECTION  lY. 


Primary  Colors. 


Red 


Yellow 


Blue 


CLASSIFICATION  OP  COLORS. 

Subdivisions. 

i  Deep  red  {crimson^  gros  rouge,  fine  red). 

<  Cherry-red. 
V  Rose-pink. 

f  Boiiton  d'or. 

<  Immortelle, 
t  Straw. 

r  Bleu  de  France  (gros  bleu), 

<  Ultramarine  (medium  blue). 
C  Celestial  blue. 


Binary  Colors  (pure) . 

Orange  (yellow 
and  red) 

Lilac  (red  and 
blue) 


Subdivisions. 


(  Deep  orange. 

■{  Medium  orange. 

V  Light  orange  (Nankeen). 

(  Violet  ^veque  (deep  lilac). 
■}  Medium  lilac. 


(  Light  lilac  (Hortensia). 

Green  (yellow  and  {  (grass-green). 

<  Medium  green  (Scheele^s  green). 
(  Light  green  (wafer-green). 


blue) 


BINARY  MIXED  COLORS. 


Orange-red, 

in  which  red 

predominates. 

Orange-yellow, 

u 

yellow 

u 

Lilac-red, 

u 

red 

u 

Lilac-blue, 

u 

blue 

u 

Greenish-yellow, 

yellow 

u 

Greenish-blue, 

u 

blue 

u 

OKIGIK,  ETC.,  OF  COLORS.  49 

Tertiary  Colors  (pure).  Subdivisions. 

f  Black  {black-black,  blue-black,  dead 
Black  {red,  yellow,  and  ^1     Hack^  bright  black), 
blue)      ...       I  Iron-gray. 

1^  Pearl-gray. 

Tertiary  Colors  (mixed.)  Subdivisions. 

Garnet  (light  green  and   (         («<=^  <^°'»'-)  ('^'"P 
<  Medium  garnet. 

(.Light  garnet  or  {tobacco). 

Bronze  (lilac,  blue,  and   \  ^f.^*^^^* 
yellow)  .       .  . 

-r,         .  J       J  ( Maroon  (brown-solitaire,  bistre). 

Brown  (orange,  red,  and  A  , 

.     .     .  i^"*^'^- 

(Hazelnut  (stone-drab). 


SECTION  Y. 

GENERAL  METHOD  OF  PREPARING  COLORS. 

We  cannot  do  better  than  to  present  to  manufac- 
turers of  colors,  the  observations  of  a  skilful  chem- 
ist, Mr.  Kletzinsky,  as  embodied  in  a  memoir,  the 
general  principles  of  which  are  here  reproduced. 

A  fact  which  appears  to  be  beyond  doubt,  says  Mr. 
Kletzinsky,  is  that,  in  the  chemical  manufacture  of 
colors,  the  wet  way  presents  many  advantages  over 
the  dry  way.  This  was  long  since  demonstrated  in 
the  manufacture  of  vermilion  by  the  wet  way,  that  is, 
by  precipitating  a  salt  of  oxide  of  mercury  with  a  sul- 
phur solution.  The  vermilion  produced  is  much 
superior  to  all  the  other  kinds  of  cinnabar  obtained 
by  sublimation  or  the  dry  way.  It  is  physically  im- 
possible by  the  dry  method,  and  by  the  mechanical 
operations  of  pulverizing,  sifting,  grinding,  and  even 
levigating  (floating),  to  arrive  at  a  molecular  com- 
minution equal  to  that  obtained  by  the  wet  way,  that 
4 


50 


MANUFACTURE  OF  COLORS. 


is,  by  the  precipitation  of  a  coloring  substance  by  the 
mixture  of  two  Hmpid  and  pure  solutions.  It  is  also 
a  well  acknowledged  fact  that  to  the  molecular  grain 
of  a  pigment,  that  is,  its  degree  of  comminution,  are 
due  its  freshness,  intensity,  tone,  body,  and  facility 
of  entering  into  mixtures. 

Therefore,  if  a  high  degree  of  comminution  is  one 
of  the  most  important  conditions  for  artistic  and  house 
painting,  it  becomes  still  more  so  when  we  have  to 
produce  given  hues  by  the  intimate  and  thorough 
mixture  of  two  or  more  colors.  For  instance,  we 
desire  to  make  a  leaf-green  by  mixing  together 
chrome  yellow  and  Berlin  blue ;  it  is  evident  that  we 
will  obtain  a  good  and  constant  green  color,  with  the 
proper  freshness  and  brightness,  only  by  a  previous 
thorough  comminution  of  each  separate  color,  and 
afterwards  by  their  intimate  admixture,  so  that  the 
blue  and  yel  low  rays  will  be  reflected  from  the  same 
point,  and  will  become  blended  and  produce  the  green 
optical  effect  on  the  eyes  of  the  observer.  As  such 
a  result  will  evidently  be  reached  more  easily  and 
cheaply  by  the  wet  way  than  by  the  long  and  tedious 
method  of  grinding,  the  principle  of  "  mixeolytical" 
colors  is  entitled  to  our  serious  attention  for  a  great 
many  chromatic  productions,  and  in  the  chemical 
manufacture  of  colors.    This  principle  is  : — 

"Choose  two  couples  of  solutions  in  such  a  man- 
ner that  each  couple  is  capable  by  itself,  when  mixed, 
of  producing  a  precipitate  possessing  all  the  necessary 
qualities  of  a  chemical  color." 

Let  a,  h  and  c,  d  be  these  two  couples  of  solutions; 
a  and  by  their  admixture,  produce  the  blue  ;  and 
G  and  under  the  same  circumstances,  result  in  yel- 
low.   If  now,  wath  the  proper  chemical  knowledge. 


ORIGrm,  ETC.,  OF  COLORS. 


51 


we  choose  such  solutions  that  a  and  c,  h  and  be 
mixed  without  decomposition,  or  production  of  in- 
desirable  precipitates,  we  have  realized  the  mixeo- 
lytical  principle,  since  the  mixture  of  the  double 
solution  a  c  with  the  double  solution  h  will  imme- 
diately give  the  precipitate  of  the  new  mixeolytical 
green  color.  Since  a  thorough  solution  is  perfectly 
homogeneous,  and  all  its  parts  have  the  same  density 
and  give  the  same  yield,  we  immediately  see  that 
the  precipitated  pigment  will  have  a  fineness  and  a 
uniformity  of  hue  and  tone  which  cannot  be  attained 
by  colors  prepared  by  mixing  and  grinding. 

The  following  mixtures  are  examples  of  the  above 
mentioned  method : — 

1. 

Mixed  double  solution  {a,  c).  Mixed  double  solution  {b,  d). 

Neutral  chromate  of  potassa,  Yellow  .  Acetate  of  lead. 
Yellow  prussiate  of  potassa,     Blue  .       .    Acetate  of  iron. 

Resulting  in  a  deep  green  color,  which  may  be  brightened  with 
nitric  acid. 

2. 

Sulphuretted  hydrogen  solu- 
tion .....    Yellow       .    Nitrate  of  cadmium. 

Yellow  prussiate  of  potassa,    Blue  .       .    Nitrate  of  iron. 
Together,  a  Scheele's  green,  which  is  not  poisonous. 

3. 

Phosphate  of  soda  (in  excess)  Blue  . 

Neutral  chromate  of  potassa,  Yellow 
Together,  a  light  leaf-green. 

4. 

Yellow  prussiate  of  potassa,  Blue. 
Chloride  of  barium      .       .  White 
Together,  a  Celestial  or  Marie-Louise 


.    Nitrate  of  copper  (in 

excess). 
.    Nitrate  of  lead. 


Perchloride  of  iron. 
Sulphate  of  ammonia. 
blue. 


52 


MANUFACTURE  OF  COLORS. 


5. 

Sulphuretted  hydrogen  (solu- 
tion) Brovm      .    Chloride  of  tin. 

Yellow  prussiate  of  potassa,     Blue  ,       .    Perchloride  of  iron. 
Together,  an  olive  green,  which  may  be  brightened  with  very 

diluted  nitric  acid. 

6. 

Sulphuretted  hydrogen  (solu- 
tion) Brown       .    Chloride  of  tin. 

Yellow  prussiate  of  potassa,     CasseVs  red.  Sulphate  of  copper. 
Together,  a  deep  bistre  color,  having  a  good  bod3\ 

These  few  examples  are  sufficient  to  give  an  idea 
of  the  almost  boundless  series  of  permutations  with 
mixeolytical  combinations.  It  is  not  only  possible 
to  multiply  the  mixtures,  but  the  relative  proportions 
of  the  solutions  may  also  be  varied  to  produce  as 
many  tones  and  hues  of  the  same  color  as  may  be 
desired,  and  that  much  more  easily  than  in  the  usual 
method  of  grinding  a  mixture  of  two  colors. 

It  is  well  understood  that  experiments  should  be 
made  with  titrated  solutions,  ^.  6.,  those  the  composi- 
tion and  yield  of  which  are  well  known,  and  also  with 
graduated  vessels  of  a  known  volume.  It  is  the  only 
way  of  reproducing  in  the  course  of  manufacture  a 
color  or  shade  which  is  satisfactory,  and  which  may 
previously  have  been  obtained  by  a  chance  hit,  or 
otherwise. 


WHITE  COLORS. 


53 


CHAPTER  11. 

MANUFACTURE  OF  COLORS. 
SECTION  L 

WHITE  COLORS. 

We  have  previously  explained  what  is  the  origin 
of  colors,  how  they  are  determined  and  classified, 
and  what  is  their  general  mode  of  preparation.  "We 
have  now  to  examine  the  processes  employed  in  the 
preparation  of  every  one  of  them,  and  we  shall  begin 
with  the  white  colors  which  are  employed  not  only 
directly  as  pigments,  but  also  for  lightening  a  great 
many  other  colors. 

For  a  long  time,  chalk  white  and  white  lead  were 
almost  the  only  whites  in  use;  but,  of  late,  the  pain- 
ter's palette  has  become  furnished  with  several  new 
white  pigments,  such  as  zinc-white,  baryta-white,  or 
blanc-fixe,  which,  from  their  peculiar  properties,  have 
been  found  very  advantageous  for  house  painting. 
We  shall  describe  their  manufacture  very  carefully, 
without,  however,  neglecting  the  description  of  the 
more  recent  processes  for  the  preparation  of  white 
lead,  processes  which  are  very  varied,  and  many  of 
which  are  now  in  use. 

§  1.  Whites  with  lime  hasis. 

1st.  Carbonate  of  lime. 

The  challc  whites,  or  carbonates  of  lime,  are  quite 
abundant ;  they  form  large  deposits  in  England,  and 


54 


MAKUFACTUHE  OF  COLORS. 


in  France,  especially  near  Rouen,  and  at  Meudon,  and 
Bougival,  near  Paris.  This  white  is  sometimes  yel- 
lowish, but  oftener  grayish  or  entirely  white.  Its 
fracture  is  earthy,  fine,  and  without  any  polish.  It 
is  soft,  without  greasy  feeling,  leaves  its  marks,  and 
adheres  to  the  tongue.  Chalk  contains  a  small  pro- 
portion of  silica,  sometimes  magnesia,  and  about  2 
per  cent,  of  clay.    There  is  iron  in  some  samples. 

Prepared  chalk  is  called  Spanish, white,  or  white  of 
Bougival,  Champagne,  or  Troyes,  according  to  the 
place  of  its  manufacture.   It  is  prepared  as  follows  : — 

After  picking  out  the  coarser  impurities,  it  is 
ground  in  a  mill  and  formed  into  rolls,  in  which  shape 
it  is  found  in  the  trade.  For  painting  purposes  it  is 
further  purified  by  stirring  in  clear  water,  allowing  it 
to  settle,  and  decanting  the  first  water,  which  is  gen- 
erally yellow  and  dirty.  The  washing  is  repeated, 
and  the  chalk  is  floated  out  into  another  vessel,  after 
passing  through  a  silk  sieve.  After  settling,  the 
water  is  decanted,  and  the  pasty  white  residue  is 
formed  into  cylindrical  rolls  10  to  12  centimetres  in 
height,  and  5  to  6  in  diameter.  These  are  allowed  to 
harden  and  dry  in  the  air,  and  are  then  ready  for 
painting,  whitewashing  ceilings,  and  for  distemper 
painting  with  size. 

Mr.  Laze  thinks  that  if  chalk  whites  are  not  sub- 
stituted for  white  lead,  it  is  due  to  the  presence  in  the 
former  of  a  certain  proportion  of  sand,  which  it  is 
difficult  to  remove.  Better  results  are  obtained  by 
sifting  than  by  simple  washing.  A  well-prepared 
chalk-white,  mixed  with  a  little  blue,  and  a  dryer, 
may  be  employed  for  oil  painting. 


"VTHITE  COLOES. 


55 


2d.  White  of  sulphate  of  lime. 

The  natural  sulphate  of  lime,  also  called  gypsum, 
or  crude  plaster  of  Paris,  is  chosen  as  pure  and  white 
as  possible,  and  then  finely  powdered  and  sifted. 
This  white  is  employed  for  the  grounds  of  paper- 
hangings,  and  also  with  size  for  house  painting. 
Some  manufacturers  adulterate  zinc-white  with  it. 

§  2.  Whites  with  lead  hasis. 

The  finest  ceruse  whites,  or  white  leads,  are  those 
manufactured  at  Krems,  or  Kremnitz  (Hungary). 
But,  as  their  preparation  requires  numerous  opera- 
tions, involving  great  labor,  and  much  time,  chemists 
have  endeavored,  by  new  and  more  rapid,  simple, 
and  cheap  processes,  to  diminish  the  time  and  cost  of 
manufacture,  without  sensibly  altering  the  quality  of 
the  products. 

In  the  order  of  their  qualities,  the  white  leads  by  the 
Holland  process  come  after  those  of  Krems,  and  next 
those  of  Clichy,  which  will  be  mentioned  further  on. 

Before  describing  various  processes  of  this  manu- 
facture, the  products  of  which  are  the  basis  of  nearly 
all  pigments  for  house  and  artistic  paintings,  we  shall 
present  a  few  general  observations  on  the  preparation 
of  white  lead  which  are  due  to  Mr.  Benson,  a  skilful 
chemist  and  manufacturer,  and  which  may  be  applied 
to  any  kind  of  white  lead,  and  are  therefore  useful  to 
manufacturers. 

The  white  lead  manufactured  by  the  Clichy  process, 
that  is,  by  the  precipitation  of  a  basic  acetate  of  lead 
with  carbonic  acid,  is  different  from  that  of  Kremnitz. 
And,  although  the.  manufacture  has  been  largely 
extended,  we  believe  that  the  processes  could  be 
improved  and  rendered  cheaper. 


56 


MANUFACTURE  OF  COLORS. 


At  the  same  time,  we  agree  with  practical  painters, 
that  the  Clichy  or  chemical  white  lead  is  less  dense 
and  possesses  less  body  than  the  Kremnitz  white. 

This  fact,  demonstrated  by  experience,  notwith- 
standing a  few  contradictions,  has  caused  several 
chemists  and  manufacturers  to  go  back  to  the  Krem- 
nitz process,  and  to  try  at  the  same  time  to  diminish 
the  length  of  the  operation.  Many  have  been  the  at- 
tempts to  employ  the  oxides  of  lead  abundantly  found 
in  the  trade,  and  to  do  away  with  the  employment  of 
boxes  which  requires  so  much  time  for  the  simulta- 
neous oxidization  and  carbonatation  of  the  lead. 

Of  litharge,  Mr.  Benson  remarks  that  it  is 'seldom 
specially  manufactured  except  for  certain  wants  in 
the  arts,  and  that  it  is  a  secondary  and  abundant  pro- 
duct obtained  in  all  the  lead  works  which  extract 
silver  from  lead. 

The'quantity  of  litharge  produced  in  England,  where 
a  great  many  lead  mines  are  in  active  operation,  is 
much  in  excess  of  the  consumption  in  the  arts.  It 
is  therefore  necessary  to  reduce  to  the  metallic  state 
that  excess  of  litharge,  notwithstanding  a  loss  of  7 
per  cent,  of  its  metal,  either  by  sublimation  or  by"" 
combination  with  the  earthy  substances  of  the  fuel 
with  which  it  is  in  contact  during  the  operation. 

Litharge  being  a  protoxide  of  lead,  it  was  believed 
that  in  order  to  transform  it  into  white  lead,  it  was 
sufficient  to  combine  it  with  carbonic  acid.  It  is  a 
mistake  which  has  given  birth  to  many  erroneous 
processes. 

In  all  of  these  processes  the  litharge  is  transformed 
into  a  basic  salt,  which  is  precipitated  in  the  form  of 
a  carbonate  by  a  stream  of  carbonic  acid.    The  pre- 


WHITE  COLORS. 


57 


cipitate  thus  obtained  is  white,  but  the  painters  who 
first  used  it  said  that  it  was  not  white  lead.  On  the 
other  hand,  several  chemists  having  found  in  it,  by 
analysis,  a  correct  relation  between  the  oxide  of  lead 
and  the  carbonic  acid,  thought  that  the  painters  were 
prejudiced. 

Dr.  Ure  appears  to  have  been  among  the  first  to 
ascertain  the  difierence  between  white  lead  and  the 
precipitated  carbonates.  White  lead  is  anhydrous, 
amorphous,  and  opaque  in  oil;  whereas  Dr.  Ure 
found  out  by  microscopic  observations  that  the  pre- 
cipitated carbonate  was  partly  crystalline  and  trans- 
lucent.* 

There  is  a  remedy  for  this  inconvenience  which 
appears  to  have  been  already  in  use  for  some  time. 
The  mode  of  operation  either  for  the  crystalline  car- 
bonate or  the  amorphous  one  is  after  all  the  same. 
In  both  cases  the  lead  is  converted  into  a  basic 
acetate,  decomposed  afterwards  by  carbonic  acid ; 
but  for  the  crystalline  carbonate  the  operation  is 
modified  by  the  pressure  of  the  liquid  in  which  it 
takes  place. 

In  one  process  the  carbonate  is  deposited  in  a  solu- 
tion, in  the  other  the  molecules  remain  all  the  time  in 
the  solid  state  and  have  no  opportunity  of  being 
symmetrically  grouped. 

Therefore,  in  order  to  produce  an  amorphous  car- 
bonate or  white  lead  from  litharge,  the  oxide  of  lead 
should  be  combined  with  such  a  small  proportion  of 
acetic  acid  that  the  resulting  basic  acetate  is  insolu- 
ble, and  there  should  be  just  enough  dampness  to 
allow  of  the  action  of  the  carbonic  acid. 

The  process  becomes  then  a  counterpart  of  that  in  ' 
general  use,  with  the  exception  that  in  this  case  the 


58 


MAOTFACTURE  OF  COLORS. 


lead  is  in  the  oxide  state,  whereas  in  the  ordinary 
method  the  oxidization  and  carbonatation  proceed 
simultaneously. 

This  process  is  actually  practised  on  a  very  large 
scale  in  a  manufactory  near  Birmingham.  The  pro- 
portion of  acetic  acid  employed  is  less  than  3^^^  of 
the  weight  of  the  litharge,  which  should  feel  simply 
moist  to  the  hand. 

The  combustion  of  coke  gives  a.  cheap  supply  of 
carbonic  acid,  and  a  powerful  stirring  machinery  is 
employed  to  hasten  the  operation  by  constantly  pre- 
senting fresh  surfaces  to  the  action  of  the  gas. 

The  result  is  that  the  operation  is  finished  in  as 
many  days  as  months  were  required  by  the  old  meth- 
ods ;  that  the  product  is  of  a  purer  white,  more  opaque 
and  with  more  body,  and  that  in  every  respect  it  is  at 
least  equal  to  the  white  lead  of  the  trade. 

Before  describing  this  process  more  completely,  it 
is  important  to  state  certain  facts  which  are  not  suflBl- 
ciently  known. 

It  is  quite  remarkable  that  the  protoxide  of  lead 
known  under  the  name  of  massicot,  and  that  called 
litharge,  behave  difierently  when  they  are  brought  up 
nearly  to  a  red  heat.  The  massicot  absorbs  oxygen 
rapidly  and  becomes  the  ordinary  red  lead  of  the  trade ; 
on  the  contrary,  this  absorption  is  very  slow,  and  some- 
times fails  entirely,  with  litharge.  On  the  other  hand, 
should  litharge  and  massicot  be  wet  with  diluted 
acetic  acid  and  exposed  to  a  stream  of  carbonic  acid, 
the  litharge  will  be  converted  into  carbonate  even 
before  the  massicot  is  acted  upon. 

Another  fact  is,  that  white  lead  and  oil  combine 
with  such  energy,  that  if  linseed  oil  is  poured  upon 
a  large  quantity  of  white  lead,  and  the  mass  allowed 


WHITE  COLORS. 


59 


to  stand  for  a  few  hours,  the  temperature  becomes  so 
high  that  the  oil  is  carbonized  and  colors  the  whole 
a  dark  black. 

It  is  also  not  generally  known  that  white  lead 
destroys  the  coloring  principle  of  linseed  oil.  If 
sulphate  of  baryta  be  mixed  with  linseed  oil,  and 
white  lead  with  a  similar  proportion  of  the  same  oil, 
the  latter  will  appear  whiter.  After  allowing  these 
two  mixtures  to  rest  for  a  few  days,  a  certain  propor- 
tion of  oil  will  rise  to  their  surface.  In  the  first  case 
the  oil  has  not  been  modified,  in  the  second  it  has 
become  almost  entirely  white,  and  has  acquired  a  cer- 
tain degree  of  rancidity. 

The  coloring  principle  of  the  oil,  as  some  persons 
might  believe,  is  not  combined  with  the  white  lead  but 
is  destroyed.  Indeed,  should  we  dissolve  the  lead  by 
means  of  some  acid,  the  oil  is  separated,  and  as  white 
as  that  which  was  on  the  top  of  the  mixture. 

Such  a  transformation  requires  a  great  excess  of 
white  lead,  and  the  precipitated  carbonates  are  not  so 
advantageous  for  painting. 

Basing  their  operations  upon  the  above  considera- 
tions, Mr.  Benson,  and  Mr.W.  Gossage,  another  distin- 
guished chemist,  have  established  a  manufacture  of 
white  lead  by  an  improved  Kremnitz  process,  which 
we  shall  now  examine. 

1st.  Kremnitz  process. 

The  manufacture  of  white  lead  by  this  improved 
process  requires  oxides  of  lead  and  acetic  acid,  or 
acetates  of  lead  and  carbonic  acid. 

The  oxides  of  lead  are  well  known  and  abundant 
in  the  trade.    Any  oxide  of  lead,  whatever  is  its  pre- 


60 


MANUFACTURE  OF  COLORS. 


paration,  which  may  be  cheaply  combined  with  car- 
bonic acid,  is  satisfactory  for  this  process. 

Among  the  various  oxides  of  lead  found  in  the 
trade,  litharge  and  massicot  are  the  best  for  this 
operation.    Red  lead  or  minium  does  not  suit  at  alL 

The  acetic  acid  employed  should  be  free  from 
coloring  substances,  which  would  discolor  the  white 
lead  and  impair  its  value.  Acetic  acid,  free  or  already 
combined  with  oxide  of  lead,  is  used.  The  acid,  as 
every  chemist  knows,  may  be  obtained  nearly  colorless 
by  the  distillation  of  vinegar,  or  by  the  decomposition 
of  the  acetate  of  lime,  or  of  any  other  combination  of 
acetic  acid  with  earthy,  alkaline,  or  metallic  bases. 

It  is  not  necessary  to  reproduce  in  this  place  the 
manner  of  effecting  these  decompositions,  which  is 
known  to  every  manufacturer.  Moreover,  such  an 
acetic  acid  is  at  the  present  day  a  product  of  the 
chemical  trade. 

When  acetate  of  lead  is  used,  the  neutral  acetate 
or  sugar  of  lead,  and  the  basic  solutions  called 
Extract  of  Saturn  and  Goulard's  water ^  are  employed. 

Carbonic  acid  may  be  obtained  by  several  methods 
actually  in  use;  but  that  which  is  preferred  on  account 
of  its  cheapness  consists  in  collecting  the  gas  result- 
ing from  the  combustion  of  charcoal,  coke,  or  anthra- 
cite. 

In  order  to  obtain  a  carbonic  acid  entirely  satisfac- 
tory for  the  manufacture  of  good  white  lead,  it  is 
absolutely  necessary  that  the  fuels  used  should  be 
entirely  deprived  of  bituminous  or  volatile  substances, 
that  is  to  say,  be  nearly  pure  carbon  with  fixed  sub- 
stances (earths). 

These  materials  are  burned  in  a  stove  or  oven,  and 
the  gases  produced,  which  are  a  mixture  of  carbonic 


WHITE  COLORS. 


61 


acid,  nitrogen,  and  undecomposed  air,  are  passed 
through  a  series  of  metallic  pipes,  so  disposed  in  the 
air  or  in  water,  that  the  gases  are  cooled  off  to  a 
moderate  temperature. 

In  order  to  arrest  any  particles  of  unhurt  carbon, 
or  any  other  substance  which  may  injure  the  color  of 
the  white  lead,  the  gases  are  passed  through  filters 
filled  with  irregular  fragments  of  lead,  such,  for 
instance,  as  may  be  obtained  by  pouring  the  molten 
metal  into  cold  water. 

A  small  stream  of  water  is  allowed  to  percolate 
through  the  lead  filters,  which,  therefore,  are  kept 
constantly  wet  during  the  passage  of  the  gas,  and  aid 
considerably  in  its  purification.  When  the  presence 
of  sulphur  is  suspected  in  the  fuel  employed,  a  small 
proportion  of  alkali  is  added  to  the  water  of  the  filters. 
Notwithstanding  this  precaution,  it  is  better  to  be 
very  particular  in  the  choice  of  the  fuel  intended  for 
the  production  of  carbonic  acid. 

The  carbonic  acid  already  in  the  atmosphere  could 
be  employed  for  carbonating  the  oxide  of  lead,  if  its 
proportion  were  not  so  small.  The  operation  would 
be  so  slow,  that,  in  every  respect,  it  is  preferable  to 
prepare  carbonic  acid  by  artificial  means. 

The  following  is  the  manner  of  manufacturing 
white  lead  with  the  above  indicated  materials: — 

If  the  oxide  of  lead  is  in  big  lumps,  it  is  necessary 
to  grind  it  down  to  a  powder,  which  needs  not  to  be 
so  very  fine.  Litharge  seldom  requires  this  operation, 
and  may  be  employed  in  the  state  in  which  it  is 
bought. 

The  oxide  of  lead  is  mixed  with  the  necessary  pro- 
portion of  acetic  acid,  or  acetate  of  lead,  and  sufficient 
water  is  added  to  make  a  consistent  paste.  This 


62 


MANUFACTURE  OF  COLORS. 


paste  is  spread  in  thin  layers  over  trays  covered  with 
sheet  lead,  and  these  trays  are  disposed  one  on  top 
of  the  other  in  a  room  for  the  purpose,  into  which 
enters  the  carbonic  acid,  either  pure,  or  mixed  with 
other  gases  which  cannot  have  any  bad  effects  upon 
the  beauty  of  the  product.  The  carbonic  acid  is 
absorbed,  and  combines  with  the  oxide  of  lead  to 
make  ceruse  or  white  lead. 

During  the  operation,  the  absorption  is  aided  and 
rendered  more  rapid,  b}^  stirring  with  rakes  the  layers 
of  lead,  and  thus  presenting  fresh  surfaces  to  the 
action  of  the  carbonic  acid. 

If  the  gas  is  dry,  or  does  not  carry  with  it  sufficient 
dampness,  a  certain  quantity  of  w^ater  is  added  to  the 
mixture  so  as  to  render  it  more  ready  to  absorb  the 
carbonic  acid.  The  proper  degree  is  easily  arrived 
at  after  several  trials  during  the  operation. 

As  the  operation  progresses,  the  oxide  of  lead,  which 
was  colored,  becomes  white;  and  when  all  of  the 
mixture  is  free  from  colored  parts,  the  treatment  is 
finished,  since  all  of  the  oxide  has  been  transformed 
into  carbonate. 

The  length  of  the  operation  varies  with  the  propor- 
tion of  acetic  acid  or  of  acetate  employed,  the  rapidity 
of  production  of  carbonic  acid,  and  the  attention 
given  in  stirring  and  in  maintaining  the  proper  degree 
of  dampness.  With  the  proportions  of  oxide  of  lead, 
acetic  acid,  or  acetate,  given  further  on,  and  a  pro- 
duction of  carbonic  acid  sufficiently  rapid,  and  the 
proper  care,  the  carbonatation  requires  from  three  to 
six  days. 

It  has  been  found  economical  to  mix  at  once  part 
of  the  oxide  of  lead  with  the  whole  of  the  proportion 
of  acetic  acid  or  of  acetate,  and  when  this  oxide  is 


WHITE  COLORS. 


63 


very  nearly  transformed  into  carbonate,  to  add  a  new 
proportion  of  oxide  without  any  more  acetic  acid  or 
acetate  of  lead.  This  new  mixture,  being  exposed  to 
the  action  of  the  carbonic  acid,  the  free  oxide  is  very 
rapidly  converted  into  carbonate.  A  new  proportion 
of  oxide  is  again  added,  and  the  operation  is  continued 
as  before,  and  always  with  a  proper  amount  of  mois- 
ture. 

These  successive  additions  of  oxide  are  repeated 
(without  more  acetic  acid  or  acetate)  until  the  pro- 
portion of  acetic  acid  or  of  acetate  is  reduced  to  one- 
fourth,  or  even  less,  of  that  which  was  in  the  primi- 
tive mixture. 

"When  the  carbonatation  is  finished,  the  mixture  is 
spread  in  a  stove-room,  and  allowed  to  dry.  Then  it 
is  ground  in  a  mill  with  water  in  the  ordinary  man- 
ner. The  ground  and  floated  product  is  dried  again, 
and  is  white  lead  for  painting  and  all  other  purposes. 

The  carbonated  mixture  may  be  ground  immediately 
after  its  removal  from  the  trays,  without  drying  it 
first;  but  the  latter  operation  improves  the  quality  of 
the  white. 

For  100  kilogrammes  of  oxide  of  lead,  we  employ 
the  same  weight  of  a  solution  of  acetic  acid  which 
contains  23  litres  of  No.  24  ov  proof  vinegar,  "When 
we  use  acetate  of  lead,  either  solid  or  in  solution,  we 
take  of  either  a  quantity  yielding  the  proportion  of 
acetic  acid  just  mentioned. 

2d.  Holland  or  Dutch  process. 

We  now  pass  to  the  details  of  the  operations  by 
the  Holland  process,  with  various  observations  and 
comparisons  made  in  several  large  French  works,  by 


64 


MAKUFACTURE  OF  COLORS. 


Mr.  E.  Combes,  and  reported  by  him  to  the  Academy 
of  Sciences. 

The  Holland  or  Dutch  process  comprises  the  fol- 
lowing operations: — 

1st.  JB  usion  and  casting  of  the  lead  in  sheets  of 
variable  thicknesses,  or  into  rectangular  or  round 
grates  (buckles). 

2d.  Alternate  layers  made  of  lead  and  stable  ma- 
nure, or  spent  tan.  The  lead  is  put  into  pots  holding 
weak  acetic  acid,  and  remains  in  the  beds  from  thirty- 
five  to  forty  days  when  stable  manure  is  employed, 
and  from  seventy  to  ninety  days  when  spent  tan  is 
used. 

3d.  Successive  uncovering  of  the  layers  of  lead,  the 
greater  part  of  which  has  become  carbonate.  Sepa- 
ration of  the  white  lead  from  the  non-corroded  metal. 
First  grinding  and  separation  of  the  blue  lead. 

4th.  Grinding  the  white  lead  with  water  under 
stones. 

5th.  Moulding  and  drying  the  floated  white  lead. 

6th.  Grinding  and  sifting  the  dry  white  lead,  and 
packing  in  barrels  that  which  is  to  be  sold  powdered. 

7th.  The  white  lead  which  is  to  be  made  into  paste 
with  oil  is  not  sifted,  biit  mixed  with  from  7  to  10 
per  cent,  of  its  weight  of  oil.  The  mixture  is  effected 
in  a  closed  stirrer,  and  then  passed  between  a  series 
of  horizontal  cast-iron  rollers.  "When  the  paste  has 
become  fine  and  homogeneous,  it  is  received  in  a  tank 
filled  with  water,  from  which  it  is  taken  and  packed 
for  sale. 

I.  The  fusion  of  the  lead  is  effected  in  cast-iron 
kettles,  and  no  dangerous  fumes  are  emitted  unless 
old  lead  or  the  residues  of  previous  operations,  still 
covered  with  carbonate,  are  melted.   In  well-disposed 


WHITE  COLORS. 


65 


works,  the  kettle  is  placed  under  a  hood  receiving  its 
draft  either  from  the  chimney  flue  of  the  furnace  itself, 
or  from  another  stack  with  a  good  draft.  The  top 
edge  of  the  furnace  is  connected  with  the  hood  by 
means  of  a  metallic  prism  or  cylinder,  having  doors 
which  are  open  for  charging  the  lead,  or  for  casting 
into  moulds  the  fused  metal.  These  precautions  seem 
to  us  sufficient  for  protecting  the  men  from  the 
noxious  fumes.  Moreover,  the  fusion  of  the  lead  is 
intermittent. 

II.  The  forming  of  the  layers  of  lead  and  stable 
manure  or  spent  tan,  presents  no  danger.  The  buckles 
or  the  thin  sheets  of  lead  rolled  into  spirals,  are  put 
into  earthenware  pots,  and  there  supported  upon  two 
or  three  projections.  The  vinegar  is  at  the  bottom 
of  the  pot. 

In  one  of  the  lead  works  of  the  department  of 
the  Seine,  the  lead  is  cast  into  rectangular  grates,  or 
buckles,  which  form  layers  upon  pots  more  shallow 
than  usual,  and  holding  the  vinegar  only. 

III.  The  separation  of  the  white  lead  from  the  non- 
corroded  metal,  and  the  first  dry  pounding  and  sift- 
ing, are  the  most  unwholesome  parts  of  the  manufac- 
ture. In  nearly  all  of  the  works  of  Paris,  the  work- 
man picks  up  by  hand  the  large  and  slightly  adher- 
ing scales  of  white  lead,  and  separates  the  remainder 
by  twisting  and  bending  in  every  direction  the  non- 
corroded  lead.  This  hand  picking  is  generally  done 
in  the  bed  itself,  and  sometimes  in  a  special  room 
where  the  whole  of  the  corroded  metal  is  carried,  in 
the  shape  it  comes  from  the  pots. 

This  picking,  however,  where  the  hands  ai-e  con- 
stantly covered  with  carbonate  of  lead,  is  not  the  most 
dangerous  part  of  the  operation,  because  the  thick 
5 


66 


MANUFACTUEE  OF  COLORS. 


scales  are  separated  without  much  dust.  But  as  the 
metallic  lead  still  retains  a  certain  quantity  of  white 
lead  strongly  adhering,  it  was  formerly  beaten  with 
a  wooden  rammer,  thus  producing  a  fine  dust,  which 
was  inhaled  by  the  workman.  This  operation  is  there- 
fore the  most  dangerous,  and  is  now  substituted  in 
several  works  by  mechanical  means,  which  imperil 
the  health  of  the  men  much  less.  The  buckles  or 
sheets  with  their  still  adherent  white  lead  are  put,  one 
by  one,  upon  an  endless  cloth,  which  carries  them  to 
an  inclined  hopper,  from  which  they  pass  between  two 
pairs  of  grooved  rollers,  and  thence  through  an  in- 
clined cylindrical  sieve.  What  passes  through  the 
holes  of  the  sieve  is  received  into  a  hopper,  which  de- 
livers it  into  a  trough  on  wheels.  The  metallic  lead 
falls  from  the  lower  opening  of  the  sieve  into  another 
trough.  The  whole  of  the  machinery  is  inclosed  in 
tight  wooden  partitions,  the  only  free  opening  of 
which  is  that  for  the  passage  of  the  endless  cloth. 
The  trough  filled  with  white  lead  is  removed  when 
the  dust  has  subsided,  and  its  contents  are  mixed 
with  the  scales  picked  up  by  hand. 

The  next  dry  grinding  is,  in  the  majority  of  cases, 
still  effected  under  vertical  stones,  rolling  upon  a 
horizontal  bed.  The  ground  lead  is  then  shovelled 
into  a  cylindrical  metallic  sieve  with  fine  holes,  and 
inclosed  in  a  wooden  box.  The  powdered  white  lead 
is  collected  at  the  bottom  of  the  box,  and  the  small 
flattened  particles  of  metallic  lead,  fall  from  the  lower 
end  of  the  sieve  into  a  special  receiver.  The  sifted 
white  lead  is  mixed  with  water,  and  thoroughly 
ground  under  mill-stones. 

In  several  manufactories  in  the  neighborhood  of 
Lille,  the  scales  of  white  lead  are  powdered  between 


WHITE  COLORS. 


67 


several  pairs  of  -horizontal  grooved  rollers.  The 
divided  substances  fall  upon  one  or  several  metallic 
sieves,  and  from  them  into  hoppers  which  conduct 
them  to  a  receiving  trough,  where  they  are  moistened 
with  a  spray  of  water.  The  metallic  lead  falls  into  a 
separate  room.  The  whole  of  the  grinding  rollers 
and  sieves  occupy  the  height  of  a  story,  and  are 
inclosed  in  wooden  partitions.  The  upper  hopper  is 
kept  filled  with  the  scales  of  white  lead,  so  as  to  pre- 
vent the  escape  of  dust.  Moreover  it  may  be  entirely 
closed  with  a  trap  door.  These  dispositions  are  a 
great  hygienic  improvement  on  the  old  process  of 
manufacture. 

In  those  works  of  the  department  of  the  Seine, 
where  the  lead  is  cast  into  grates  or  buckles,  and  not 
into  sheets,  the  separation  of  the  white  lead  and  its 
dry  pulverization  and  sifting  are  effected  by  mechani- 
cal apparatus  following  one  another,  and  placed  in 
closed  rooms. 

The  first  room  contains  a  series  of  three  pairs  of 
grooved  rollers  which  separate  the  white  lead  from 
the  non-corroded  metal,  and  another  series  of  three 
pairs  of  smooth  rollers  which  grind  the  scales  of  white 
lead.  There  is  an  opening  at  each  opposite  extremity 
of  the  room:  one  for  the  passage  of  the  endless  cloth 
carrying  the  corroded  buckles ;  and  the  other  for  the 
escape  of  the  cleaned  lead  which  slides  upon  a  sheet- 
iron  apron,  perforated  with  holes  and  made  to  shake 
by  machinery.  These  grates  or  buckles  of  metallic 
lead  are  received  by  one  or  two  workmen,  who  put 
apart  the  thin  ones  for  remelting,  and  separate  and 
straighten  those  which  are  thick  enough  to  go  into 
the  beds  again. 

The  scales  of  white  lead,  separated  by  the  grooved 


68 


MANUFACTURE  OF  COLORS. 


rollers,  fall  upon  an  endless  cloth  placed  under  the 
shaking  apron  of  perforated  sheet  iron,  and  are  brought 
upon  the  three  pairs  of  smooth  rollers,  between  which 
they  are  powdered.  The  powder  falls  upon  an  inclined 
plane,  which  conducts  it  to  a  pit,  from  which  it  is 
taken  up  by  an  endless  bucket  strap  (inclosed  in 
tight  wooden  troughs),  and  carried  to  the  top  of  an 
upper  room,  where  the  metallic  sieve  for  the  separa- 
tion of  the  blue  from  the  white  lead  is.  The  metallic 
portions  are  received  in  a  distinct  place,  and  the  white 
lead  falls  on  to  the  floor  of  the  room,  from  which  it 
is  removed  when  the  dust  has  settled.  In  this 
operation,  the  men  who  receive  the  buckles  of  lead 
from  the  rollers,  are  still  exposed  to  the  dust  of  the 
white  lead,  and  remain  but  a  few  days  at  that  work. 

To  sum  up :  the  separation  of  the  scales  of  white 
lead,  and  their  dry  grinding  and  sifting,  cannot  be 
considered  a  wholesome  manufacture  anywhere,  al- 
though there  have  been  many  improvements  made 
and  hygienic  precautions  taken  in  most  of  the  works 
we  have  visited.  Certain  manufacturers  have  tried  to 
obviate  the  not  very  great  danger  of  picking  white 
lead  with  the  hand,  by  furnishing  the  men  with 
gloves.  This  precaution  seems  to  us  insufficient, 
because  gloves  are  often  an  impediment  to  the  work, 
and  the  men  will  be  tempted  to  leave  them  off. 

In  the  works  where  the  separation  of  the  white 
lead  from  the  non-corroded  metal  is  not  done  by 
hand,  there  is  still  danger  of  inhaling  fine  white  lead 
dust,  when  the  thick  buckles  are  straightened  and 
struck  with  the  mallet.  Lastly,  a  very  fine  lead  dust 
escapes  from  the  rooms  containing  the  grinding 
apparatus,  either  from  the  apertures  for  the  inlet  or 


WHITE  COLORS. 


69 


outlet  of  the  substances,  or  from  the  openings  cut  in 
the  wooden  partitions  for  the  passage  of  the  shafting. 

The  causes  of  danger  would  quite  cease  to  exist, 
if  the  separation  of  the  scales  of  white  lead,  their 
grinding  and  sifting,  were  effected  underwater;  or, 
at  least,  if  the  white  lead  and  the  metallic  residues 
were  subjected  to  sprays  of  water  immediately  after 
they  leave  the  grinding  apparatus.  Such  is  the  mode 
of  operation,  as  we  learn  from  data  of  Mr.  Le  Play, 
in  the  English  white  lead  works.  There,  all  the 
metallic  residues  are  cast  anew,  before  returning  to 
the  beds.  We  call  the  attention  of  manufacturers  and 
of  the  public  administration  to  this  method,  which 
presents  no  serious  difficulties,  since  it  is  generally 
practised  in  England.  The  white  lead  is  also  de- 
prived, by  washing,  of  certain  soluble  salts  which 
may  injure  its  purity;  moreover  the  subsequent  ope- 
ration is  always  effected  with  the  aid  of  water. 

IV.  The  white  lead  is  mixed  with  water  in  troughs, 
so  as  to  form  a  soft  paste  which  passes  successively 
through  several  horizontal  mill-stones  before  it  is 
thoroughly  comminuted.  This  wet  grinding  is  abso- 
lutely without  danger,  since  the  men  do  not  touch 
the  white  lead  with  their  hands,  but  carry  it  in  scoops 
or  ladles. 

Y.  In  all  the  works  which  we  have  visited,  the 
soft  paste  of  white  lead  is  poured  into  conical  earthen- 
ware pots,  which  are  dried  in  a  stove  room.  The 
greater  part  of  the  water  is  expelled,  and  the  blocks 
becoming  contracted,  are  easily  removed  from  the 
pots.  Their  thorough  drying  is  finished  in  another, 
or  the  same,  stove  room. 

The  sides  of  the  pots  are  coated  with  white  lead, 
which  is  generally  scraped  off  with  an  iron  tool.  This 


70 


MANUFACTURE  OF  COLORS. 


operation  is  performed  by  women  or  children,  and  is 
not  without  inconvenience.  It  is  remedied  in  certain 
works,  by  washing  the  pots  in  water;  but  this 
involves  more  labor  and  expense.  Part  of  the  white 
lead  is  sold,  after  drying,  in  the  shape  of  conical 
blocks,  which  are  wrapped  in  paper  and  put  into 
barrels,  care  being  taken  not  to  break  them.  This 
handling  of  white  lead  is  not  entirely  wholesome, 
although,  with  the  proper  precautions,  it  is  not  dan- 
gerous. 

In  an  establishment  of  the  department  of  the  Seine, 
the  white  lead  is  not  put  into  pots ;  but  the  soft  paste 
is  poured  upon  a  cloth  which  is  then  folded  so  as  to 
form  a  square  flat  bag.  Several  such  bags,  separated 
by  square  wooden  trays,  are  afterwards  squeezed  in  a 
hydraulic  press,  which  expels  the  greater  part  of  the 
water.  After  unfolding  the  cloth,  the  block  of  white 
lead  is  cut  into  prisms  or  bricks  having  siiflScient 
consistency  to  be  carried  immediately  into  the  drying 
room.  A  small  proportion  of  the  product  of  these 
works  is  sold  in  the  shape  of  dry  prisms;  but  their 
packing  in  barrels  is  not  done  with  the  same  care  as 
with  the  conical  blocks,  because  the  products  go  to 
consumers  sufficiently  learned  to  know  that  the  ex- 
ternal shape  of  white  lead  is  no  proof  of  its  good  or 
bad  quality.  The  bricks  or  prisms  of  white  lead  are 
compressed  in  the  barrel  by  the  cylinder  of  a  hydraulic 
press. 

VI.  The  greater  part  of  the  white  lead  in  lumps 
requires  to  be  ground  and  sifted  again  before  it  is 
ready  for  sale.  This  second  grinding,  in  the  majority 
of  works,  is  still  done  with  vertical  stones  rolling 
upon  a  stone  bed.  The  ground  stuff  is  shovelled  into 
the  hopper  of  a  cylindrical  silk  sieve,  inclosed  in  a 


WHITE  COLORS. 


71 


wooden  box,  where  the  fine  white  lead  falls.  That 
which  has  not  passed  through  the  meshes  of  the  sieve 
is  collected  in  another  box,  and  ground  anew.  The 
sifted  white  lead  is  removed  from  its  box,  after  the 
dust  has  subsided,  and  packed  in  barrels  either  by 
shaking,  or  by  a  slight  ramming. 

The  grinding,  sifting,  and  packing  of  the  dry  white 
lead  by  the  foregoing  method,  are  evidently  danger- 
ous on  account  of  the  dust  floating  in  the  workshop. 
The  inconveniences  can  be  considerably  diminished, 
by  inclosing  within  wooden  partitions  the  mill-stones 
and  the  sieve,  as  is  practised  in  lead  works  at  Lille, 
where  the  vertical  stones  have  been  replaced  by  hori- 
zontal ones  of  white  marble.  Each  pair  of  stones  is 
within  a  drum,  on  top  of  which  is  a  hopper  filled  with 
the  lumps  of  white  lead,  coarsely  broken  by  means  of  a 
rotary  grooved  cone  placed  within  it.  The  powdered 
material  is,  by  centrifugal  force,  projected  against  the 
drum,  and  falls  by  two  diametral  openings  into  the 
sieve  below,  which  is  also  well  inclosed.  In  order  to 
prevent  the  dust  from  flying  during  the  packing,  the 
white  lead  is  compressed  by  means  of  a  wooden  disk, 
of  nearly  the  same  diameter  as  that  of  the  barrel,  and 
pressed  downwards  by  a  screw. 

YII.  The  works  in  the  neighborhood  of  Lille 
sell  the  greater  part  of  their  products  in  the  shape 
of  powder  or  lumps  :  that  is,  about  one-third  in  lumps 
and  two-thirds  in  powder.  A  manufacturer  of  the  de- 
partment of  the  Seine  has  all  the  apparatus  necessary 
for  grinding  the  white  lead  in  oil,  and  seven-eighths  of 
his  production  is  sold  as  a  paste  holding  from  7  to  9 
per  cent,  of  oil.  The  prisms  of  white  lead  are  ground 
in  a  kind  of  cofi^ee  mill,  which  delivers  a  not  very  fine 
powder.    The  powder  is  then  put  into  a  horizontal 


72 


MANUFACTURE  OF  COLORS. 


cylinder,  with  a  certain  proportion  of  oil,  and  mixed 
by  means  of  iron  paddles  fixed  to  the  shaft  running  the 
length  of  the  cylinder.  From  thence  the  paste  passes 
between  a  series  of  cast-iron  rollers,  and  becomes  fine 
and  homogeneous.  More  oil  is  added  if  necessary. 
The  finished  paste  is  kept  under  water  in  large  tubs, 
from  whence  it  is  taken  for  packing. 

Thus,  when  white  lead  is  ground  in  oil  in  good 
apparatus,  like  those  we  have  seen,  in  operation,  it  is 
not  necessary  to  grind  it  into  a  fine  powder,  and  we 
avoid  one  of  the  most  unwholesome  operations.  It  is 
therefore  highly  advantageous  that  all  the  white  lead 
(and  we  believe  that  by  far  the  greater  part  of  the 
white  lead  is  always  ground  in  oil)  should  be  mixed 
with  oil  in  the  works  themselves,  instead  of  in  many 
separate  shops,  where  the  men  are  subject  to  lead 
colics,  from  want  of  proper  precautions  and  apparatus. 
It  appears  certain,  from  what  we  have  seen  in  a  lead 
works  at  Birmingham,  and  from  the  data  of  Mr.  Le 
Play,  that  the  English  manufactories  deliver  the 
greater  part  of  their  products  iixthe  shape  of  a  paste 
holding  from  8  to  9  per  cent  of  oil.*  It  is  highly 
desirable  that  the  same  thing  should  be  done  in 
France. 

In  the  majority  of  white  lead  works,  certain 
hygienic  precautions  are  required  of  the  workmen. 
Thus,  when  they  leave  work,  they  wash  their  hands, 
arms,  and  faces.  Soap,  fuller's  earth,  and  sometimes 
tubs  filled  with  a  solution  of  sulphide  of  potassium, 
are  put  at  their  disposal.    In  one  of  the  Paris  works, 

*  In  England,  at  least  in  several  works,  there  are  three  brands 
of  white  lead  paste;  the  first  is  pure  white  lead  with  from  8  to  9 
per  cent,  of  oil;  the  other  two  qualities  contain  sulphate  of  bar^'ta 
in  the  proportions  of  about  15  and  25  per  cent. 


WHITE  COLORS. 


73 


tubs  for  sulphuretted  baths  are  placed  in  a  room  near 
the  boilers  which  furnish  the  necessary  steam. 

The  men  are  alternately  put  to  the  unwholesome 
parts  of  the  work,  and  do  not  remain  long  there.  A 
cloak-room  where  the  men  leave  their  working  clothes 
after  work,  exists  in  several  factories.  Nearly  every- 
where they  receive  gratuitously  the  first  cares  of  a 
physician  who  is  paid  by  the  manufacturer. 

The  work-rooms  are  generally  large  and  well  ven- 
tilated, especially  where  the  dry  white  lead  is  ground 
and  sifted.  However,  the  walls  and  the  shafting  are 
covered  with  white  lead  dust,  even  when  the  grinding 
apparatus  is  inclosed;  and  this  demonstrates  that  the 
grinding  operation  is  not  entirely  innocuous. 
^  Our  own  observations  and  the  data  we  have  col- 
lected, allow  us  to  state  that  the  general  manufacture 
of  white  lead  is  not  so  dangerous  as  some  persons  may 
believe,  and  this  is  proved  by  statistics  collected  in 
the  hospitals  of  Paris  for  several  years  past.  There 
are,  however,  great  differences  in  regard  to  salubrity, 
between  the  different  works  we  have  visited.  No- 
where have  the  old  processes  failed  to  receive  some 
improvement;  but,  even  the  most  perfect  works  are 
open  to  some  objections  in  regard  to  the  separation 
of  the  white  lead  from  the  non-corroded  metal,  and 
the  dry  grinding  and  sifting,  which  precedes  the  wet 
grinding  between  the  horizontal  stones. 

Before  proceeding  further,  we  believe  that  it  is  now 
desirable  to  add  a  few  theoretical  considerations  on 
the  manufacture  of  white  lead,  which  are  due  to  Mr. 
Pelouze,  who  has  paid  great  attention  to  that  sub- 
ject. 

"  The  Holland  process,"  says  Mr.  Pelouze,  "  which 
has  been  carried  on  at  Lille,  where  it  has  become  a 


74 


MANUFACTURE  OF  COLORS. 


prominent  manufacture,  consists  in  exposing  sheet 
lead  to  the  vapors  of  vinegar  and  to  the  gases  of  stable 
manure.  The  vinegar  used  is  that  made  from  inferior 
beer,  and  contains  but  a  small  proportion  of  acetic 
acid.  From  the  examination  I  have  made  of  that 
vinegar,  and  with  the  numbers  furnished  to  me  by 
MM.  Lefebre  and  D6coster,  manufacturers  of  white 
lead  at  Lille,  the  weight  of  real  acetic  acid  is  less  than 
1^  per  cent,  of  the  weight  of  lead  employed,  and  in 
good  corroding  operations  nearly  the  whole  of  the 
metal  is  transformed  into  white  lead.  Mr.  Graham, 
in  England,  has  arrived  at  similar  results,  and  with 
even  a  less  percentage  of  acetic  acid.  It  is  therefore 
impossible  that  the  carbonic  acid  of  the  white  lead 
should  be  derived  from  the  decomposition  of  ther 
vinegar. 

"  Moreover,  manufacturers  are  well  acquainted  with 
the  fact,  that  no  white  lead  is  obtained  when  drafts 
are  not  established  between  the  different  parts  of  the 
beds. 

"The  theory  of  this  process  is  therefore  very  simple. 
The  air  produces  the  oxidization,  and  the  vinegar, 
volatilized  by  the  heat  of  the  fermenting  manure, 
unites  with  the  oxide  of  lead,  being  then  displaced 
by  the  carbonic  acid  disengaged  by  the  manure.  A 
considerable  portion  of  the  acetic  acid  is  found  in  the 
unwashed  white  lead  made  by  the  Holland  process. 

"  I  believe  that  such  is  the  reaction,  and  since  I 
have  left  Lille  where  I  was  able  to  study  that  manu- 
facture, I  have  held  this  theory  as  being  the  most 
rational. 

"  I  have  made  an  experiment  which  well  demon- 
strates the  mode  of  action  of  the  vinegar  in  the  forma- 
tion of  white  lead.    I  have  compounded  an  artificial 


WHITE  COLORS. 


75 


atmosphere  of  oxygen  and  carbonic  acid,  and  in  it  I 
have  placed  a  piece  of  sheet  lead  exposed  to  the  vapors 
of  vinegar  in  a  cup  underneath.  After  three  months 
the  lead  was  covered  with  a  crust  of  white  lead,  the 
proportion  of  which  was  in  the  ratio  of  the  oxygen 
and  carbonic  acid  absorbed,  whereas  most  of  the 
vinegar  was  found  in  its  previous  state.  The  pro- 
portion of  acetic  acid  causing  the  transformation  into 
white  lead  was  so  small  that  it  could  not  be  ascer- 
tained. 

"  Another  very  curious  experiment,  in  my  own  opin- 
ion, fully  demonstrates  the  true  action  of  acetic  acid 
in  the  formation  of  white  lead,  and  the  necessity  of 
employing  in  that  manufacture  an  acid  which  may 
produce  with  oxide  of  lead  a  basic  or  subsalt  which 
may  be  decomposed  by  carbonic  acid. 

*'If  in  the  preceding  experiment  we  substitute  for 
the  vinegar  formic  acid  which  does  not  produce  basic 
salts  with  oxide  of  lead,  there  is  no  white  lead  formed 
even  after  a  contact  of  several  years  of  the  vapors  of 
formic  acid,  the  lead  and  the  gases,  oxygen  and  car- 
bonic acid.  Formic  acid,  however,  is  very  near  to 
acetic  acid  in  its  affinities  and  its  volatility ;  but  as 
it  does  not  make  basic  salts  with  oxide  of  lead,  and 
as  the  neutral  formiate  of  lead  is  not  decomposed  by 
carbonic  acid,  it  is  therefore  unsuitable  for  the  manu- 
facture of  white  lead." 

Mr.  Hochstetter  thought,  notwithstanding  the  pre- 
ceding observations,  that  it  was  still  necessary  to 
directly  ascertain  whether  air  was  the  only  oxidizing 
agent  in  the  manufacture  of  white  lead,  especially  in 
the  Holland  process. 

Adding  to  his  own  experience  the  explanations  of 
the  above-mentioned  chemists,  he  attributes  the  form- 


76 


MANUFACTURE  OF  COLORS. 


ation  of  white  lead  to  two  distinct  causes  in  the 
Holland  process  : — 

First,  to  the  subacetate  of  lead  which  results  from 
the  contact  of  the  air,  lead,  and  acetic  acid.  This 
salt  is  decomposed  into  carbonate  of  lead  and  neutral 
acetate  in  an  atmosphere  saturated  with  carbonic  acid 
and  dampness. 

Second,  to  the  decomposition  of  the  neutral  acetate 
by  wet  carbonic  acid.  Carbonate  of  lead  is  produced 
and  acetic  acid  is  displaced. 

For  a  long  time  it  has  been  stated  that  white  lead 
is  not  a  neutral  carbonate  of  lead,  but  a  subcarbonate 
or  a  combination  of  neutral  carbonate  with  a  six 
basic  acetate.  The  examination  of  this  question  was 
of  practical  interest,  since  the  lesser  consistency  of 
the  Holland  white  lead  was  due  in  the  opinion  of  Mr. 
Mulder  to  the  presence  of  an  hydrated  oxide  of  lead. 

The  author  has  therefore  repeated  the  analyses  of 
the  latter  chemist  nearly  in  the  same  manner,  and  the 
results  have  been  as  follows  : — 

Krems^  White. 

Washed.    Atoms.  Calculated. 

Oxide  of  lead  ....  88.n  83.9^7  8  84.06 
Water  .  .  .  .  .  1.01  0.84  1  0.85 
Carbonic  acid         .       .       .    15.06       15.03        T  14.05 


99.84  99.84 

Precipitated  White  Lead  of  Magdeburg. 

Oxide  of  lead  ....    85.93       ...        3  86.3 

Water     .       .       .       .       .     2.01       ...        1  2.3 

Carbonic  acid        .       .*       .    11.89       ...        2  11.3 

White  Lead  of  Unknown  Manufacture. 

Oxide  of  lead  ....    86.40       ...        3  86.3 

Water  2.13       ...        1  2.3 

Carbonic  acid         .       .       .    11.52       ...        2  11.3 


WHITE  COLORS. 


77 


Krems^  White. 

Washed.    Atoms.  Calculated. 

Oxide  of  lead  ....    86.25       ...        3  86.3 

Water  2.21       ...        1  2.3 

Carbonic  acid        .       .       .    11.37       ...        2  11.3 

White  Lead  Prepared  by  the  Author  in  Imitation  of  the 
Holland  Process. 

Oxide  of  lead    84.42        8  84.6 

Water   1.36        1  0.8 

Carbonic  acid    14.45        7  14.5 

These  experiments  prove,  indeed,  that  none  of  the 
samples  examined  are  a  pure  neutral  carbonate,  and 
that  the  missing  carbonic  acid  is  replaced  by  water. 
It  seems,  therefore,  that  white  leads  may  often  be 
variable  combinations  of  carbonate  and  of  hydrate  of 
lead.    We  shall  again  examine  this  point  further  on. 

The  author  has  prepared  a  white  lead  by  pre- 
cipitating the  subacetate  of  lead  with  carbonic  acid 
until  the  liquor  began  to  be  acid.  The  precipitate 
perfectly  washed  with  boiling  water,  gave : — 

Washed.    Atoms.  Calculated. 

Oxide  of  lead        .      ..       .       .       .    86.02        3  86.4 

Water  2.44        1  2.3 

Carbonic  acid   11.45        2  11.3 

Corresponding  to  the  formula  2(PbO.C02)  +  PbO.HO. 

This  white  lead  suspended  in  water  and  submitted 
for  a  long  time  to  a  stream  of  carbonic  acid  does  not 
change.  But  if  a  few  drops  of  acetic  acid  are  added 
before  the  treatment  with  carbonic  acid,  it  becomes 
neutral  carbonate. 

The  author  has  prepared,  by  precipitation,  nume- 
rous samples  of  white  lead,  and  all  had  the  composi- 
tion of  the  French  white  lead.  However,  he  does 
not  decide  on  the  question  of  the  body  or  covering 
property,  between  the  white  lead  prepared  by  the  Hoi- 


78 


MAlSrUFACTURE  OF  COLORS. 


land  and  French  processes.  By  microscopic  exami- 
nation no  sensible  difference  of  texture  was  detected, 
nor  was  any  sample  with  a  crystalline  texture.  If 
the  good  quality  of  white  lead  be  due  to  the  absence 
or  to  the  presence  of  but  a  slight  proportion  of 
hydrate,  it  is  now  possible  to  obtain,  by  precipitation, 
a  white  lead  answering  to  this  condition. 

3d.  The  French  or  Glichy  Process^  by  Thenard. 

Thenard  was  the  first  to  point  out  a  process  for  the 
manufacture  of  white  lead,  which  was  applied  later 
by  Mr.  Eoard  in  a  large  establishment  near  Paris,  the 
products  of  which  are  known  under  the  name  of 
ClicJiy  white  lead.  The  chemical  reactions  on  which 
this  process  is  based  are  as  follows : — 

If  a  solution  of  basic  acetate  of  lead,  sometimes 
called  Extract  of  Saturn^  be  treated  with  carbonic 
acid,  part  of  the  oxide  of  the  salt  is  converted  into 
carbonate  of  lead,  and  the  remainder  becomes  neutral 
acetate.  By  adding  a  new  proportion  of  litharge  or 
oxide  of  lead  to  the  solution  of  neutral  acetate,  this 
becomes  basic  again  by  the  solution  of  the  oxide. 
"We  see,  therefore,  that  these  reactions  permit  of  the 
manufacture  of  white  lead  by  a  continuous  and 
economical  production  of  basic  acetate. 

Without  thoroughly  considering  all  the  manipula- 
tions of  this  process  we  shall  indicate  the  mode  of 
operation. 

A  solution  of  basic  acetate  of  lead,  marking  from 
16°  to  18°  Be.,  is  made  by  boiling  a  solution  of  neu- 
tral acetate  (sugar  of  lead)  with  very  finely  powdered 
oxide  of  lead  (litharge).  There  is  no  difficulty  in 
this  operation. 

"When  the  litharge  has  become  dissolved,  and  the 


WHITE  COLORS. 


79 


basic  solution  is  well  saturated,  the  liquor  is  decanted 
from  the  impurities  in  the  litharge  or  the  acetate, 
into  a  closed  vessel.  Then  the  carbonic  acid  is 
introduced,  which  gas  may  be  produced  by  several 
methods,  such  as  the  calcination  of  chalk  or  the  com- 
bustion of  carbon.  At  all  events  the  gas  should  be 
previously  well  washed,  so  as  not  to  add  impurities 
to  the  white  lead. 

As  soon  as  it  is  ascertained  that  all  the  basic 
excess  of  oxide  of  lead  is  transformed  into  carbonate, 
the  liquors  are  allowed  to  settle.  The  carbonate 
falls  to  the  bottom,  and  the  supernatent  solution  of 
neutral  acetate  is  decanted  to  be  boiled  again  with 
oxide  of  lead,  and  become,  as  we  have  said,  basic 
acetate. 

There  is,  however,  at  each  operation  a  certain  loss 
of  neutral  acetate,  which  must  be  replaced  and  ren- 
dered as  small  as  possible  by  careful  manipulation. 

The  settled  carbonate  of  lead  is  first  washed  with 
a  small  proportion  of  water,  which  is  added  to  the 
decanted  solution  of  acetate.  The  washing  is  then 
continued  with  larger  quantities  of  water,  which  are 
thrown  away,  since  they  are  too  poor  in  acetate. 
The  paste  of  white  lead  is  put  into  pots,  and  dried  in 
the  stove  room. 

This  Clichy  white  lead  is  in  impalpable  powder  and 
as  white  as  snow ;  but,  compared  with  those  of  Krems 
and  Holland,  it  has  less  density  and  body,  that  is, 
covers  less. 

The  manufacture  of  white  lead,  by  the  Th^nard 
process,  has  been  established  at  Portillon,  near  Tours, 
by  MM.  Pallu  and  Delaunay,  with  a  perfect  under- 
standing of  its  theory.  Thanks  to  a  report  made  in 
1856  to  the  "Societe  d'Encouragement"  by  MM.  A. 


80 


MANUFACTURE  OF  COLORS. 


Chevalier,  F.  Barral,  and  Gaultier  de  Claubry,  we  are 
enabled  to  explain  this  manufacture. 

Preparation  of  the  oxide  of  lead, — The  works  of 
Portillon,  as  stated  by  the  above  delegates,  contain 
five  furnaces  with  double  fire-places,  four  of  which 
are  in  constant  operation,  and  use  bituminous  coal  as 
fuel.  The  furnaces  are  built  directly  in  the  rock,  and 
calcine  1800  kilogrammes  of  lead  at  each  operation. 
The  leads  employed  bear  the  best  brands  of  Andalusia 
and  of  England,  and  are  analyzed  at  the  works  so  that 
the  best  only  may  be  received.  The  bed  of  each  furnace 
is  built  with  fire-brick  holding  as  little  silica  as  possi- 
ble. The  shape  is  nearly  circular,  about  3.40  metres 
in  diameter,  and  with  two  lateral  fire-places.  It  is 
hollow,  so  as  to  retain  the  molten  metal.  The  vault 
is  surbased,  and  60  centimetres  (0.60  metre)  is  the 
greatest  distance  between  the  bed  and  the  ceiling  of 
the  vault. 

During  the  heating,  the  gases  of  the  combustion 
escape  through  an  opening  or  hood,  placed  in  front  of 
the  aperture  used  for  charging  the  metal  or  extracting 
the  oxide.  This  hood  connects  with  an  upper  fur- 
nace where  the  transformation  of  the  oxide  of  lead 
into  red  lead  takes  place. 

Twelve  hours  are  required  for  oxidizing  1500  kilo- 
grammes of  lead  ;  but  the  oxide  still  contains  a  large 
proportion  of  metal  or  hlue  lead,  which  is  separated 
and  returns  to  the  calcining  furnaces.  Half  of  the 
oxide  produced  is  for  the  manufacture  of  white  lead, 
and  the  other  half  for  that  of  red  lead. 

Manufacture  of  the  white  lead, — The  oxide  of  lead 
intended  for  the  preparation  of  white  lead  is  moistened 
with  water,  and  spread  over  a  wooden  floor  above  two 
saturating  pans  lined  with  copper.    These  pans  are 


WHITE  COLORS. 


81 


supplied  with  stirrers  composed  of  a  wooden  frame 
with  bronze  projections,  which  reach  to  about  1  or  2 
centimetres  from  the  bottom.  One  of  the  pans  is 
raised  above  the  other,  so  that  the  excess  of  liquid  in 
the  upper  one  may  run  by  a  spout  into  the  lower  one. 
The  latter  pan,  at  the  middle  of  its  height,  is  connected 
with  a  duplex  bronze  pump. 

The  two  pans  are  filled  with  water  rendered  acid 
by  about  one-fortieth  of  pure  pyroligneous  acid 
marking  30  acetimetric  degrees.  While  the  stirrers 
are  in  motion,  a  certain  proportion  of  damp  oxide  of 
lead  is  poured  in,  and  becomes  dissolved  in  part.  The 
pump  is  then  set  to  work,  and  forces  the  solution  into 
three  large  tanks,  lined  with  copper,  placed  in  an  upper 
story,  and  which  connect  with  each  other.  These  tanks 
have  stirrers  like  those  of  the  saturating  pans,  and 
which  are  kept  in  motion  during  the  whole  operation. 

Besides  the  pipes  for  conducting  the  liquors,  these 
three  apparatus  are  provided  with  pipes  and  inverted 
gutters,  perforated  with  numerous  small  holes,  through 
which  a  continuous  stream  of  carbonic  acid  escapes. 
The  average  specific  gravity  of  the  solution  is  5°  Be. 

During  this  operation  the  pump  takes  from  the 
saturating  pans  the  solution  of  basic  acetate,  and 
carries  it  into  the  precipitating  tanks  where  it  is 
brought  into  contact  with  the  carbonic  acid.  The 
white  lead  is  immediately  formed,  and  the  liquid, 
which  must  still  retain  a  certain  proportion  of  basic 
acetate,  passes  into  the  settling  tanks  where  the  white 
lead  becomes  deposited.  The  liquor  then  goes  back 
to  the  saturating  tanks,  and  the  operation  begins 
anew.  It  is,  as  we  see,  a  system  of  circulation  in 
which  machinery  performs  most  of  the  work,  and 
hand  labor  is  reduced  to  a  minimum. 
6 


82 


MANUFACTURE  OF  COLORS. 


After  a  certain  length  of  time,  the  settling  tank  is 
sufficiently  filled  with  white  lead,  that  is,  when  this 
material  reaches  the  level  of  the  overflow.  The  solu- 
tion is  then  made  to  pass  into  other  vessels  and  the 
white  lead  is  washed  in  washing  tanks ^  which  are  pro- 
vided with  wooden  horizontal  stirrers  having  a  rotary 
motion. 

The  settled  white  lead  is  covered  with  twice  its 
volume  of  pure  water  and  stirred.,  Three  washings 
take  place,  and  at  each,  the  material  is  allowed  to 
deposit,  and  the  water  above  is  decanted. 

The  white  lead  is  then  conducted  into  large  basins 
built  of  porous  stones,  which  absorb  part  of  its  damp- 
ness. After  a  few  days,  the  material  is  divided  into 
blocks  which  are  still  quite  wet,  and  which  are 
pounded  by  wooden  vertical  stamps  falling  into  a 
wooden  trough  inclined  from  the  front  backwards. 

This  stamping  renders  fluid  the  white  lead  which 
appeared  half  dry  before.  The  stuff  is  then  put  into 
small  movable  boxes,  holding  about  400  kilogrammes, 
and  which  are  carried  to  the  drying-room.  It  is 
sufficient,  for  filling  the  pots,  to  open  and  close  the 
trap-doors  at  the  bottom  of  these  boxes. 

When  the  white  lead  is  to  be  sold  in  powder,  the 
stamped  paste  is  run  into  wooden  frames,  which  are 
set  upon  a  brick  platform  heated  underneath.  When 
dry,  it  is  put  upon  a  distributor  similar  to  that  used 
for  red  lead,  but  larger,  and  which  projects  it  upon  a 
sheet-iron  ventilator  having  four  wings.  The  venti- 
lator is  inclosed  within  cast-iron  plates,  and  is  followed 
by  a  rectangular  trough  of  the  same  metal,  about  1 
metre  long.  At  the  top  end  of  the  trough  there  is  a 
sheet-iron  pipe  35  centimetres  in  diameter,  8  metres 
long,  and  nearly  vertical,  which  communicates  at  its 


WHITE  COLORS. 


83 


upper  end  with  a  large  sheet-iron  chamber,  to  the  bot- 
tom of  which  are  fixed  two  funnels  or  hoppers  closed 
by  lateral  sliding  plates.  Below  the  opening  of  the 
vertical  pipe,  and  in  the  cast-iron  trough,  there  is  a 
east-iron  hexagonal  prism  which  rotates  and  pulver- 
izes the  coarse  portions  of  white  lead  which  have  not 
reached  the  upper  chamber,  and  delivers  them  back  to 
the  ventilator.  The  white  lead  deposited  in  the  iron 
chamber  above  is  in  impalpable  powder. 

The  distributor,  like  that  for  red  lead,  has  an  aspi- 
rator, so  that  there  is  no  danger  of  dust  being  inhaled 
by  the  men. 

The  above  operations  apply  to  the  preparation  of 
white  lead  in  lumps  and  in  powder,  as  is  generally 
required  by  the  trade.  However,  for  several  years 
past,  part  of  the  white  lead  has  been  ground  in  oil, 
which  is  a  hygienic  progress,  since  numerous  cases  of 
lead  colic  have  been  observed  among  those  who 
grind  white  lead  in  the  shops  of  color  dealers. 

The  grinding  of  white  lead  in  oil  is  done  at  the 
works  of  Portillon  as  follows :  the  stamped  and  still 
damp  material  is  introduced  into  a  kneading  machine 
with  the  given  proportion  of  oil,  and  soon  transformed 
into  dough,  which  is  removed  through  a  side  opening. 
The  paste  is  then  ground  between  metallic  rollers 
heated  by  steam,  and  the  water  expelled.  After 
another  passage  through  an  ordinary  grinding  appa- 
ratus, the  paste  is  put  into  zinc  cans  soldered  or  closed 
tight. 

The  carbonic  acid  used  for  the  manufacture  of 
white  lead,  and  which  passes  through  the  solution  of 
subacetate,  is  produced  by  the  combustion  of  cheap 
charcoal  dust,  cemented  into  bricks  by  means  of  a 
small  quantity  of  clay.    The  gas  is  aspirated  from  the 


84 


MANUFACTURE  OF  COLORS. 


combustion  furnace  by  means  of  a  series  of  inverted 
drums  plunging  into  water,  and  which  act  as  pumps. 

Here  are  also  a  few  data  on  a  modification  of  this 
process,  practised  in  England,  and  the  description  of 
which  is  due  to  Mr.  Preisser. 

The  lead  is  smelted  in  a  cast-iron  kettle  with  a 
spout,  which  delivers  it  upon  the  bed  of  a  large 
reverberatory  furnace,  in  which  air  is  constantly  in- 
jected by  a  ventilator.  The  lead  becomes  divided, 
offers  a  large  surface  to  the  air,  and  runs  into  a 
channel  the  lateral  sides  of  which  are  perforated  with 
small  holes.  The  lead  is  oxidized,  and  the  litharge 
escapes  through  small  apertures  which  may  be  opened 
at  the  same  time.  The  silver,  if  any,  remains  at  the 
bottom  of  the  channel.  This  mode  of  preparing 
litharge  is  very  easy  and  rapid. 

The  litharge  is  then  finely  divided,  and,  after  being 
moistened  with  1  per  cent,  of  acetate  of  lead  dissolved 
in  water,  is  put  into  horizontal  troughs,  closed  on  top 
and  communicating  one  with  the  other.  A  stream 
of  impure  carbonic  acid,  produced  by  the  combustion 
of  coke  in  a  reverberatory  furnace,  with  air  projected 
by  two  powerful  centrifugal  ventilators,  passes  all 
the  while  through  the  layers  of  oxide.  The  pressure 
exerted  by  the  ventilators  is  sufficient  to  overcome 
the  resistance  of  the  layers  of  litharge.  The  gases 
are  cooled  in  pipes  immersed  in  water. 

In  order  to  bring  all  the  particles  of  oxide  into 
contact  with  the  carbonic  acid,  and  aid  the  combina- 
tion, a  system  of  rakes,  moved  by  machinery,  keeps 
the  mass  constantly  stirred. 

The  white  lead  obtained  by  this  process  is  good  for 
painting,  and  is  perfectly  white.  It  covers  well,  and  is 


WHITE  COLOKS. 


85 


preferred  in  England  to  that  prepared  in  the  wet 
way,  which  contains  crystalline  particles. 

4th.  Pattinson  Process, 

By  means  of  a  chemical  reaction,  by  double  ex- 
change of  bases  and  acids,  Mr.  Pattinson  obtains 
carbonate  of  lead  on  the  one  hand,  and  on  the  other  a 
solution  of  lime  salt,  the  nature  of  which  depends  on 
that  of  the  lead  salt  employed.  The  salts  which  he 
perfers  are  the  chloride  and  the  nitrate. 

Here  are  the  chemical  phenomena  observed  when 
carbonate  of  lime  and  chloride  of  lead  react  on  each 
other.  Equivalent  proportions  of  these  substances 
are  triturated  together,  that  is,  140' parts  of  chloride 
of  lead,  and  50  of  carbonate  of  lime,  and  sufficient 
water  is  added  to  make  a  thin  paste.  After  a  certain 
length  of  time,  indications  of  chemical  reaction  ap- 
pear, the  paste  becoming  thicker,  drier,  and  nearly 
hard.  Afterwards  the  solid  mass  begins  to  deli- 
quesce, and  soon  resolves  itself  into  a  concentrated 
solution  of  chloride  of  calcium,  and  a  white  precipi- 
tate of  carbonate  of  lead  mixed  with  undecomposed 
carbonate  of  lime  and  chloride  of  lead. 

After  decanting  the  solution  of  chloride  of  calcium, 
and  replacing  it  by  pure  water,  the  former  decompo- 
sition continues ;  and  if  this  operation  be  repeated 
several  times,  accompanied  by  trituration  of  the  sub- 
stances, the  carbonate  of  lime  and  the  chloride  of 
lead  are  quite  entirely  decomposed,  and  the  residue 
is  nearly  pure  carbonate  of  lead.  This  complete  de- 
composition requires  from  seven  to  fifteen  days,  and 
still  there  remain  traces  of  chloride  of  lead  and  car- 
bonate of  lime,  which  may  be  detected  by  chemical 
analysis. 


86 


MANUFACTURE  OF  COLORS. 


The  reaction  is  quite  similar,  either  in  its  nature 
or  in  the  length  of  time  required,  when  we  triturate 
together  equivalent  proportions  of  nitrate  of  lead 
(166  parts)  and  of  carbonate  of  lime  (50  parts). 
Moreover,  it  has  been  ascertained  that  the  decomposi- 
tion of  the  nitrate  or  chloride  of  lead  is  more  rapid 
when,  instead  of  pure  water,  a  solution  of  carbonic 
acid  gas  is  employed.  Indeed,  carbonate  of  lime  is 
soluble  in  water  impregnated  with  carbonic  acid,  and 
is  in  a  form  which  renders  the  reaction  more  i*apid 
and  complete.  As  soon  as  the  soluble  carbonate  of 
lime  has  been  decomposed  the  free  carbonic  acid 
causes  the  solution  of  another  proportion,  which  is 
decomposed  in  its  turn,  and  so  on,  the  operation 
being  continued  with  the  same  proportion  of  carbonic 
acid  until  the  decomposition  is  complete,  if  the  mix- 
ture has  been  made  in  accurate  chemical  proportions. 

But  as  the  water  impregnated  with  the  carbonic  acid 
becomes  by  degrees  a  more  and  more  concentrated 
solution  of  lime  salt,  it  is  preferable,  towards  the  end 
of  the  operation,  to  replace  it  by  fresh  water  holding 
carbonic  acid.  It  is  even  better  to  change  the  water 
several  times,  so  as  to  insure  the  decomposition  of 
the  entire  carbonate  of  lime  employed.  It  is  also 
necessary  to  stir  the  contents  frequently. 

After  these  observation  we  now  pass  to  the  prac- 
tical process  of  the  white  lead  manufacture. 

The  mill  in  use  is  similar  to  that  employed  in 
pottery  and  earthenware  factories  for  grinding  flint 
stones  in  water.  A  strong  wooden  tank,  bound  with 
iron,  has  its  bottom  filled  with  blocks  of  quartz  or  of 
French  burr,  cemented  together,  and  with  a  level  sur- 
face. Other  large  stone  blocks  are  made  to  revolve 
over  the  lower  surface,  and  grind  to  a  fine  powder 


WHITE  COLOES. 


87 


the  hard  and  brittle  substances  which  have  been 
put  into  the  mill  with  the  addition  of  water.  For  our 
purpose  the  running  stones  need  not  be  so  heavy  as  in 
pottery  works,  because  the  materials  do  not  require 
the  same  degree  of  comminution.  "We  should  avoid 
employing  iron  whenever  this  metal  may  be  in  con- 
tact with  the  ground  substances,  and  use  copper  for 
the  metallic  parts  of  the  inside  of  the  tank. 

In  a  mill  of  that  kind,  4  metres  in  diameter  and  1 
metre  high,  the  charge  is  1066  kilogrammes  of  chlo- 
ride of  lead  and  380  kilogrammes  of  carbonate  of 
lime,  the  best  of  which  is  washed  chalk.  As  much 
water  is  added  as  will  just  not  run  over  by  the  motion 
of  the  stones,  and  the  grinding  operation  lasts  six 
hours.  After  that  the  tank  is  almost  entirely  filled 
with  water,  and  allowed  to  stand  till  the  next  day, 
when  the  deposit  is  found  to  be  carbonate  of  lead 
mixed  Avith  the  undecomposed  carbonate  of  lime  and 
chloride  of  lead.  The  supernatant  liquor  is  a  clear 
and  concentrated  solution  of  chloride  of  calcium, 
nearly  free  from  lead,  and  which  is  decanted  by  means 
of  a  siphon  or  a  stopcock.  A  new  quantity  of  water 
is  put  into  the  mill,  and  the  grinding  is  repeated  for 
a  few  hours,  followed  by  a  settling  and  a  decanting 
on  the  next  day,  and  so  on,  until  from  the  seventh 
to  the  fifteenth  day,  when  the  solution  has  no  taste,  and 
the  decomposition  is  complete. 

The  white  substance  at  the  bottom  of  the  mill 
is  nearly  pure  carbonate  of  lead,  with  but  traces  of 
chloride  of  lead  and  carbonate  of  lime,  and  is  removed, 
dried,  and  prepared  in  the  ordinary  manner  for  the 
trade. 

A  modification  of  this  process  consists  in  adding, 
at  first,  an  excess  of  chloride  of  lead,  that  is,  1264 


88 


MANUFACTURE  OF  COLORS. 


kilogrammes  for  380  kilogrammes  of  carbonate  of 
lime,  and  grinding,  settling,  and  decanting  the  liquors 
until  all  the  carbonate  of  lime  is  decomposed,  which 
is  ascertained  by  the  absence  of  a  bitter  taste  in  the 
solution.  Then  the  excess  of  chloride  of  lead  is 
transformed  into  carbonate  by  the  addition  of  about 
200  kilogrammes  of  soda  crystals,  or  an  equivalent 
proportion  of  carbonate  of  potassa.  The  liquor 
should  remain  slightly  alkaline.  The  grinding  is 
continued  until  all  the  chloride  of  lead  has  become 
carbonate;  and,  afterwards,  the  chloride  of  sodium 
or  potassium  is  removed  by  washing.  In  this  manner 
the  length  of  the  operation  is  shortened  and  the  car- 
bonate of  lead  is  purer. 

The  inconvenience  of  this  method  is  that,  beside 
the  greater  expense  due  to  the  alkaline  carbonate,  a 
small  proportion  of  chloride  of  lead  is  dissolved  in 
the  washing  liquors  before  the  carbonate  of  lime  is 
throughly  decomposed.  It  is  true  that  the  lead  may 
be  recovered  from  the  last  washings  by  a  precipitation 
with  a  sulphide  of  potassium  or  sodium. 

If,  instead  of  grinding  in  pure  water,  we  use  a 
solution  of  carbonic  acid,  the  operation  is  performed 
as  follows:  A  vessel,  barrel-shape,  which  may  be 
of  wood,  copper,  or  lead,  and  about  0.75  metre  in 
diameter  and  1.20  in  height,  is  tightly  bound  with  iron, 
and  has  its  heads  sufficiently  stout  to  resist  the  neces- 
sary pressure.  It  revolves  upon  two  trunnions,  one  of 
which  carries  a  fast  and  a  loose  pulley,  so  that  motion 
may  be  given  or  arrested  at  will.  The  other  trunnion 
is  hollow,  and  has  a  stopcock  communicating  by  a 
universal  joint  with  the  pump,  which  forces  the  car- 
bonic acid  into  the  vessel. 

Through  a  side  opening,  50  to  75  millimetres  in 


WHITE  COLORS. 


89 


diameter,  70  kilogrammes  of  chloride  of  lead  and  25 
kilogrammes  of  carbonate  of  lead  are  introduced. 
The  vessel  is  then  nearly  filled  with  pure  water,  the 
opening  is  closed  with  a  screwed  plate,  and  carbonic 
acid  is  forced  through  the  hollow  trunnion  under  a 
pressure  of  from  four  to  five  atmospheres.  After 
closing  the  stopcock,  the  barrel  is  set  in  motion,  and 
revolves  about  twenty  times  per  minute.  The  sub- 
stances begin  to  react  one  upon  the  other:  the  car- 
bonic acid  with  which  the  water  is  saturated  dissolves 
the  carbonate  of  lime  and  presents  it  to  the  chloride 
of  lead  in  such  a  state  that  the  decomposition  is  im- 
mediate. The  reaction  is  continued  for  two  or  three 
days,  and  is  then  so  near  the  end  that  but  little 
carbonate  of  lime  and  chloride  of  lead  remain  unde- 
composed ;  and,  in  their  stead,  there  is  carbonate  of 
lead  and  a  concentrated  solution  of  chloride  of  cal- 
cium. The  motion  of  the  barrel  is  then  discontinued, 
and,  when  the  contents  have  had  time  to  settle,  the 
clear  liquid  is  siphoned  off  through  the  lateral  open- 
ing and  replaced  by  fresh  liquor,  which  is  saturated 
with  carbonic  acid  as  previously.  The  barrel  is  made 
to  revolve  for  two  or  three  days  more,  when  the  decom- 
position is  completed,  and  the  carbonate  of  lead  ob- 
tained requires  but  a  thorough  washing  and  drying. 

In  this  second  mode  of  operation  an  excess  of 
chloride  of  lead  may  be  employed  to  promote  a  more 
rapid  decomposition  of  the  carbonate  of  lime.  The 
remaining  chloride  of  lead  is  decomposed  in  the  barrel 
with  a  slight  excess  of  an  alkaline  carbonate,  as  we 
have  already  explained. 

When  nitrate  of  lead  is  employed  the  operation  is 
the  same  as  with  the  chloride,  whether  we  use  pure 
water  or  that  saturated  with  carbonic  acid.  The 


90 


MANUFACTURE  OF  COLORS. 


equivalent  proportions  are  for  the  stone  mill — 1264 
kilogrammes  of  nitrate  of  lead  and  380  kilogrammes 
of  carbonate  of  lime,  and,  for  the  revolving  vessel,  83 
kilogrammes  of  nitrate  of  lead  and  25  kilogrammes  of 
carbonate  of  lime. 

In  either  case  the  substances  are  allowed  to  react 
upon  each  other  until  the  decomposition  is  complete. 
The  resulting  white  lead  is  then  washed,  dried,  and 
packed  in  the  usual  manner. 

Sometimes,  also,  a  solution  of  carl3onate  of  lime  in 
water  saturated  with  carbonic  acid  is  effected  in  the 
revolving  apparatus,  and  is  poured  into  tanks  holding 
the  solution  of  either  chloride  or  nitrate  of  lead.  A 
pure  carbonate  of  lead  is  immediately  precipitated. 

We  shall  now  quote  from  Mr.  F.  Heeren,  a  manu- 
facturing chemist,  who  has  carefully  studied  a  pecu- 
liar white  lead,  prepared  by  another  Pattinson  process. 

"The  white  lead  of  Mr.  Pattinson  is  distinguished 
from  the  ordinary  kind  by  its  composition,  which  is 
a  basic  chloride  and  an  oxychloride  of  lead,  instead 
of  a  combination  of  oxide  of  lead  with  carbonic  acid. 

"Mr.  Pattinson  prepares  his  white  lead  from  crude 
galena  (sulphide  of  lead)  abundant  in  England,  and 
which  often  contains  silver.  This  latter  metal  is 
entirely  collected,  and  the  sulphur  is  also  employed. 

"  The  finely  powdered  galena  is  heated  in  closed 
lead  vessels  with  concentrated  hydrochloric  acid, 
which  is  produced  in  large  quantities  in  soda  works, 
and  which  is  very  cheap.  By  this  treatment  the 
sulphur  is  transformed  into  hydrosulphuric  acid 
(sulphuretted  hydrogen)  which  is  burned  in  the 
furnace  of  sulphuric  acid  chambers,  and  thus  assists  in 
the  production  of  sulphuric  acid.  The  lead  is  trans- 
formed into  chloride,  and  as  this  salt  is  but  slightly 


WHITE  COLORS. 


91 


soluble,  large  volumes  of  boiling  water  are  employed 
in  order  to  separate  the  sulphide  of  silver  contained 
in  the  gelena.  The  boiling  solution  of  chloride  of 
lead,  in  order  to  pass  to  the  basic  state,  needs  to  be 
mixed  with  lime-water.  It  is  absolutely  necessary 
that  the  mixing  should  be  effected  very  rapidly  in 
order  to  obtain  the  basic  chloride  of  lead  in  the  shape 
of  an  exceedingly  fine  powder  which  covers  well.  A 
slow  and  gradual  mixing  results  in  a  crystalline  pre- 
cipitate which  does  not  cover  well. 

"  Another  condition  is  that  the  proportion  of  lime 
should  be  exactly  calculated  for  neutralizing  half  of 
the  chlorine  of  the  chloride  of  lead,  and  that  the  pre- 
cipitated basic  salt  should  contain  equal  atoms  of 
chloride  and  of  oxide  of  lead.  The  clear  solution  of 
lime  is  in  one  tank,  the  hot  one  of  chloride  of  lead  is 
in  another  tank,  and  they  are  mixed  together  by 
regulating  their  running  into  a  third  tank  by  means 
of  stopcocks. 

"One  inconvenience  of  this  manufacture  is,  that, 
the  chloride  of  lead  being  but  slightly  soluble  even  in 
boiling  water,  very  large  vessels  are  needed,  and  the 
consumption  of  fuel  to  heat  the  water  is  considerable. 
A  neutral  chloride  of  lead  requires  about  twenty-two 
times  its  own  weight  of  boiling  water  to  be  dissolved, 
and  theoretically  for  fifty  kilogrammes  of  Pattinson's 
white  lead  1219  litres  of  boiling  water  are  required 
for  the  chloride  of  lead,  plus  4420  litres  for  the  lime, 
altogether  5639  litres,  occupying  a  cube  having  1.80 
metres  in  every  direction. 

"  When  experimenting  with  this  process  on  a  small 
scale,  I  have  found  out  another  difficulty,  e.,  when 
powdered  galena  is  treated  with  hydrochloric  acid, 
the  surface  of  the  grains  is  soon  coated  with  chloride 


92 


MANUFACTURE  OF  COLORS. 


of  lead  which  arrests  the  action  of  the  acid.  The 
entire  galena  is  dissolved  only  when  a  large  excess  of 
hydrochloric  acid  is  employed  suflScient  to  dissolve 
the  whole  of  the  chloride  of  lead  formed.  However, 
the  expense  of  such  an  excess  of  acid  may  be  avoided 
by  decanting  the  hot  solution  into  another  vessel  as 
soon  as  the  action  ceases,  and  allowing  it  to  become 
cold  and  to  deposit  the  chloride  of  lead.  The  cold 
acid  is  decanted  and  used  again  upon  the  galena,  and 
when  saturated  with  chloride  let  to  cool  off. 

The  chloride  of  lead  thus  obtained  and  drained, 
is  washed  with  small  proportions  of  cold  water  in 
order  to  remove  the  free  acid  and  any  iron  salt  which 
otherwise  would  discolor  the  white  lead.  It  is  then 
dissolved  in  boiling  water. 

"  Several  samples  of  Pattinson's  w^hite  lead  which 
I  have  examined,  are  not  pure  white,  but  with  a 
slight  brownish  shade  which  is  scarcely  sensible  when 
a  small  proportion  of  black  or  blue  is  added  to  them. 
On  the  other  hand,  it  covers  particularly  well.  I  have 
ground  equal  parts  of  Pattinson's  and  Krems  white 
lead  with  equal  proportions  of  oil,  and  I  painted  with 
them  surfaces  of  equal  area;  the  Pattinson  white 
lead  had  evidently  the  best  covering  power.  It  is 
very  bulky,  possesses  great  body,  and  absorbs  a  large 
proportion  of  oil." 

5th.  Woolrich  Process. 

Commercial  lead  is  granulated  by  means  similar 
to  those  used  for  making  lead  shot,  and  the  granules 
are  put  into  a  cylindrical  or  hexagonal  stoneware 
vessel,  which  may  be  made  to  revolve  upon  a  central 
shaft  passing  through  two  holes  at  the  opposite  ends 
of  the  vessel.    During  the  motion  the  lead  is  kept 


WHITE  COLORS. 


93 


constantly  wet  with  a  neutral  solution  of  acetate  of 
lead  of  specific  gravity  1.6.  By  the  mutual  attrition 
of  the  granules  of  lead,  aided  by  the  above  solution, 
particles  become  separated  which  are  washed  out 
every  twelve  hours.  Fresh  proportions  of  granulated 
lead  moistened  as  we  have  said,  are  then  added  to 
make  up  the  loss  by  attrition  and  decomposition.  The 
separate  particles  with  the  washings  are  collected  in 
a  closed  vat,  through  which  is  injected  carbonic  acid 
produced  by  the  combustion  of  charcoal  or  coke.  The 
substances  are  kept  stirred  by  proper  machinery,  and 
there  is  produced  a  carbonate  of  lead  which  settles  in 
a  few  hours,  and  is  removed  after  the  washing  liquors 
have  been  decanted. 

A  hexagonal  vessel  55  centimetres  in  diameter, 
and  1.60  metre  high,  will  hold  from  400  to  500 
kilogrammes  of  lead. 

6th.  Versepuy  Process. 

An  Italian  once  made  the  observation  that  when 
granulated  lead  is  comminuted  by  friction,  it  becomes 
transformed  into  white  lead  by  absorbing  carbonic 
acid.  Mr.  Versepuy  thus  states  the  improvements 
he  has  brought  to  that  system  : — 

"  Fragments  of  lead  are  put  into  a  stone  cylinder 
(made  of  Volvic  lava  if  possible)  and  covered  with 
water.  After  twelve  hours  of  rotary  motion,  the 
metallic  mud  is  poured  into  a  wooden  tub  having  a 
wooden  stirrer  in  the  middle  and  two  ventilators  on 
the  upper  surface  with  the  proper  capping  to  prevent 
the  liquor  from  running  over. 

"The  inside  surfaces  of  the  stone  cylinder  become 
coated  with  a  layer  of  white  lead  which  prevents 
further  waste  of  stone,  and  is  believed  to  act  as  a 


91 


MANUFACTURE  OP  COLORS. 


leaven  for  the  oxidization  of  the  molecules  of  lead 
during  the  further  operations. 

"  It  is  not  necessary  in  a  regular  operation  to 
employ  lead  in  a  thorough  state  of  division. 

"Water  is  necessary  for  separating  the  particles  of 
lead  produced  by  mutual  attrition. 

"  The  metallic  mud  should  be  removed  from  the 
stone  cylinder  and  from  the  undivided  lead,  in  order 
to  aid  its  oxidization  by  an  energetic  stirring. 

"  The  carbonic  acid  of  the  air  is  sufficient  to  pro- 
duce the  carbonate,  and  no  advantage  has  been  found 
in  the  use  of  artificial  carbonic  acid  or  of  an  atmos- 
phere of  this  gas  in  the  tub.  The  same  may  be  said 
of  an  addition  of  acetic  or  nitric  acid  or  of  one  of 
their  salts. 

"  This  process,  as  we  see,  is  very  easy  and  economi- 
cal. The  operation  is  not  complicated  by  the  addi- 
tion of  any  chemical  agent,  and  mechanical  manipu- 
lation alone  is  sufficient  to  bring  about  the  transfor- 
mation of  the  metal  into  white  lead. 

"In  this  process  everything  favors  the  manufac- 
turers of  lead  who  own  the  raw  material  and  may 
utilize  the  water-power  generally  abundant  in  the 
neighborhood  of  mines." 

Since  giving  this  description,  Mr.  Versepuy  has 
improved  his  processes,  which  are  thus  described  in 
his  patent  of  July  15th,  1846 : — 

"  I  propose  to  oxidize  lead  at  the  ordinary  tempera- 
ture, under  the  influence  of  an  energetic  stirring,  and 
of  the  intimate  and  simultaneous  contact  of  the  metal 
with  air  and  water.  The  oxide  thus  obtained  is  car- 
bonated by  a  liquid  constantly  saturated  with  car- 
bonic acid. 

"The  process  maybe  divided  into  three  distinct 
operations : — 


WHITE  COLORS. 


95 


"First,  the  division  of  the  lead  to  as  great  an  ex- 
tent as  practicable,  in  order  to  obtain  large  surfaces 
of  corrosion. 

"  Second,  the  oxidization  of  the  lead  by  the  oxygen 
of  the  air,  and  the  immediate  removal  of  the  pellicle 
of  oxide  by  washing  and  stirring.  The  oxidization 
may  be  aided  by  an  energetic  oxidizing  agent,  an 
acid  for  instance. 

"  Third,  the  carbonatation  of  the  oxide  by  its  con- 
tact with  carbonic  acid  gas  obtained  by  any  desired 
method. 

"  I  know  that  similar  processes  have  already  been 
tried,  but  the  experimenters  have  never  succeeded, 
because  they  were  not  sufficiently  aware  of  the  im- 
portance of  each  operation  and  of  its  results.  They 
have  never  employed  a  current  of  air  sufficiently 
energetic  to  furnish  enough  oxygen  to  the  metal — or 
an  auxiliary  oxidizing  agent — or  a  subsequent,  dis- 
tinct, and  well-conducted  carbonatation. 

"  Here  is  the  mode  of  operation  which  I  found  to 
succeed  best : — 

"1.  The  lead  is  melted  in  a  closed  furnace,  which 
is  a  protection  against  the  fumes  being  inhaled  by 
the  men,  and  poured  into  cold  water  through  a  fine 
metallic  sieve.  Small  and  light  granules  are  thus 
obtained  which  present  a  great  surface  to  corrosion. 

"II.  The  granulated  lead  is  placed  in  the  cylinder 
F  (Fig.  1),  with  one-fifth  of  its  weight  of  water,  and 
a  small  proportion  of  some  oxidizing  agent.  A  pipe 
K  brings  into  the  cylinder  a  brisk  current  of  air, 
forced  in  by  means  of  a  fan  or  of  a  screw-blowing 
machine  like  Fig.  2.  The  pipe  k  passes  through  the 
stuffing-box  T,  and  the  air  is  divided  by  a  rose  at  J, 
before  it  escapes  from  the  cylinder  at  j'.    A  rapid 


96 


MANUFACTURE  OF  COLORS. 


rotary  motion  is  imparted  to  the  cylinder,  the  inside 
metal  parts  of  which  are  of  lead,  in  order  not  to  injure 
the  oxide.    The  friction  of  the  granules  together  and 


Fig.  1. 


against  the  sides  of  the  cylinder,  at  the  same  time 
with  the  chemical  reaction  which  takes  place,  gives  an 
increase  of  temperature  of  from  55°  to  60°  C,  and  it 

is  important  to  keep  it  up 
^*  by  making  the  operation 

continuous.  The  rotary 
motion  of  the  cylinder 
should  not  be  too  rapid, 
so  as  not  to  keep  together 
by  centrifugal  force  the 
mass  of  granules,  which, 
on  the  contrary,  should 
fall  and  describe  a  curve. 
This  operation  lasts  about  twenty-four  hours,  and 
then  the  thick  and  yellowish  liquid  is  removed  from 
the  cylinder. 

"  III.  The  above  mixture  is  diluted  with  twice  its 
weight  of  water,  and  poured  into  the  cylinder  m, 


WHITE  COLORS. 


97 


which  may  be  of  wood  lined  with  lead.  An  inner 
stirrer  presents  fresh  surfaces  to  the  action  of  carbonic 
acid,  and  makes  at  least  one  hundred  and  fifty  evolu- 
tions per  minute.  A  pipe  d  brings  in  the  carbonic 
acid  gas  produced  by  any  desired  method,  and  forced 
in  by  mechanical  action. 

"It  is  possible  to  use  the  small  proportion  of  car- 
bonic acid  held  in  atmospheric  air,  in  which  case  the 
earbonatation  is  slow,  or  the  carbonic  acid  gas  em- 
anating from  mineral  springs,  or  from  the  reaction  of 
an  acid  upon  a  carbonate,  or  that  produced  in  a  lime- 
kiln or  from  a  fireplace.  In  the  latter  cases,  a 
screw-blowing  machine.  Fig.  2,  is  very  suitable,  since 
the  gases  are  cooled  and  separated  from  the  ashes  in 
the  water  of  the  apparatus. 

"In  from  fifteen  to  thirty  minutes,  according  to 
the  quantity  of  material  in  operation,  the  action 
is  complete,  the  mass  of  oxide  becomes  white,  and 
there  is  an  elevation  of  temperature  of  fi'om  60  to 
65°  G.  The  white  lead  and  water  may  then  be  re- 
moved. 

"  It  is  well  understood  that  the  stream  of  carbonic 
acid  escaping  from  this  cylinder  passes  into  other 
similar  apparatus  to  complete  its  condensation. 

"  The  white  lead  thus  produced  is  by  the  usual 
processes  brought  into  the  commercial  shape." 

In  an  addition  to  his  patent  (July  15th,  1847),  Mr. 
Versepuy  expresses  his  disbelief  in  the  usefulness  of 
an  auxiliary  oxidizing  agent. 

7th.  Wood,,  Benson,,  and  H.  Gruneberg  Processes. 

We  owe  to  Mr.  "Wood  a  process  for  manufacturing 
white  lead,  which  consists  in  introducing  granulated 
lead  and  water  into  a  revolving  and  horizontal  hex- 
7 


98 


MANUFACTURE  OF  COLORS. 


agonal  box,  the  two  ends  of  which  have  openings  for 
the  circulation  of  the  air.  A  hyd rated  protoxide  of 
lead  is  formed,  which  is  removed  through  a  side  open- 
ing jDrovided  with  a  sieve,  and  which  is  saturated 
separately  with  carbonic  acid. 

Mr.  Gruneberg,  after  a  careful  study  of  this  method, 
found  out  that  a  cause  of  failure  was  the  formation, 
in  the  revolving  apparatus,  of  a  peroxide  of  lead  con- 
jointly with  the  desired  protoxide.  By  the  treatment 
with  carbonic  acid,  the  peroxide  remains  as  such,  and 
colors  the  white  lead  a  pink  or  reddish  hue.  As  proof 
that  this  coloration  is  due  to  the  peroxide,  the  white 
lead  is  dissolved  in  diluted  nitric  acid,  and  if  the 
washed  residue  be  treated  with  hydrochloric  acid  and 
a  gold  leaf,  the  latter  becomes  dissolved,  thus  show- 
ing the  presence  of  a  peroxide. 

^N^evertheless.  Mr.  Gruneberg  uses  for  his  process 
the  Wood  apparatus,  that  is  to  say,  a  hexagonal  re- 
volving prism  made  of  stoneware  unacted  upon  by 
acids.  During  the  operation,  the  lead  is  submitted 
to  the  simultaneous  action  of  atmospheric  air,  acetic 
acid,  and  carbonic  acid  gas.  The  atmospheric  air 
enters  through  openings  on  the  heads  of  the  prism, 
and  the  acetic  and  carbonic  acids  through  the  hollow 
axis. 

In  order  to  aid  oxidation,  the  inside  of  the  appara- 
tus is  provided  with  projecting  ribs,  which  cause  the 
lead  to  fall  down  and  to  present  fresh  surfaces  to  the 
action  of  the  air.  By  means  of  the  simultaneous  re- 
action of  the  air,  of  the  solution  of  acetate  of  lead,  and 
of  carbonic  acid,  the  process  resembles  the  Holland 
method,  except  that  it  takes  place  in  a  revolving 
apparatus.  The  conditions  are  excellent,  since  the 
film  of  white  lead  on  the  surface  of  the  metal  is  con- 


WHITE  COLORS. 


99 


stantly  removed  and  fresh  metallic  surfaces  are  pre- 
sented to  the  chemical  agents.  Eight  days  are  suffi- 
cient by  this  method  for  completely  transforming 
into  white  lead  a  given  weight  of  lead  which  would 
require  two  months  by  the  Holland  process. 

The  mutual  friction  of  the  lead,  and  the  chemical 
reactions  which  take  place,  cause  an  elevation  of 
temperature  which  is  very  advantageous  and  prevent 
any  crystallization  of  the  white  lead.  This  pigment, 
washed  out  now  and  then  from  the  apparatus,  is  so 
fine  that  the  ordinary  operations  of  grinding  and 
floating  are  entirely  unnecessary. 

The  mechanical  motion  added  to  the  chemical 
reactions,  gives  in  one  operation  a  product  which 
simply  needs  washing  and  drying  to  be  ready  for 
sale.  The  formation  of  a  peroxide  is  also  avoided, 
since,  as  soon  as  the  protoxide  is  formed  it  changes 
to  a  basic  acetate,  and  has  no  time  to  absorb  a  larger 
proportion  of  oxygen. 

However  simple  this  process  may  appear,  it  never- 
theless presents  many  practical  difficulties,  and  the 
oxidation  requires  a  great  deal  of  care. 

The  introduction  of  air  and  carbonic  acid  should 
be  effected  in  certain  fixed  proportions.  An  excess  of 
carbonic  acid  does  not  produce  the  neutral  carbonate 
of  lead  (PbO.CO')  and  the  liquid  in  the  apparatus  is 
all  in  a  foam  which  envelops  the  lead  and  prevents 
the  access  of  the  air.  Thus,  no  oxidation  takes  place, 
and  the  yield  of  white  lead  becomes  low. 

We  should  endeavor  to  produce  the  compound 
2(PbO.CO')  +  PbO.HO,  and,  on  that  account,  the 
substances  inside  of  the  revolving  apparatus  should 
be  kept  in  the  basic  state.  This  condition  is  ascer- 
tained by  trying  the  liquors  with  yellow  turmeric 


100 


MAOTFACTURE  OF  COLOKS. 


paper,  which  should  turn  brown.  A  basic  milk  of 
white  lead  does  not  foam,  but  runs  smooth  and  leaves 
the  granules  of  lead  perfectly  clean  and  ready  to  be 
oxidized. 

There  should  never  be  so  much  carbonic  acid  as 
completely  to  decompose  the  basic  acetate  of  lead,  but 
merely  the  proportion  necessary  to  saturate  a  quantity 
corresponding  to  the  oxide  formed.  But  as  it  is  not 
easy  to  remain  always  within  the  proper  limits,  it 
will  be  well  frequently  to  test  the  liqnors  with  the 
turmeric  paper. 

The  basic  excess  of  hydrated  oxide  of  lead  should 
not,  however,  remain  with  the  white  lead,  because  it 
renders  the  oil  paints  made  with  this  pigment  yehow. 
Indeed,  this  oxide  PbO.HO  forms  with  the  fatty 
acids  of  the  oil,  a  colored  soap  which  requires  a  long 
time  to  become  decomposed  by  the  action  of  light  and 
the  carbonic  acid  of  the  air.  By  its  transformation 
into  carbonate  of  lead,  the  desired  whiteness  re- 
appears. 

Moreover,  a  white  lead  with  an  excess  of  PbO.HO 
has  a  great  specific  gravity,  and  as  demonstrated 
by  analysis,  has  a  composition  near  to  the  formula 
3(PbO.CO')  +  2(PbO.HO).  This  excess  of  oxide  is 
removed  by  adding  to  the  thin  paste  of  white  lead, 
enough  acetic  acid  to  prevent  the  turmeric  paper 
from  becoming  brown.  The  white  lead  has  then  the 
composition  2(PbO.CO^)  +  PbO.HO  which  is  a 
durable  combination  without  basic  properties. 

As  this  operation  cannot  be  well  done  in  the  re- 
volving apparatus  itself,  the  white  lead  is  washed  off 
with  a  very  weak  solution  of  subacetate  of  lead,  into  a 
special  tub  where  it  is  treated  with  acetic  or  carbonic 
acid.    The  neutralized  white  lead  is  then  allowed  to 


WHITE  COLORS. 


101 


settle  at  the  bottom  of  other  tubs,  and  the  solution  of 
subacetate  is  employed  again  for  the  oxidizing  opera- 
tion. The  deposit  is  finally  washed  with  pure  water 
and  drained  in  a  centrifugal  apparatus. 

The  ordinary  centrifugal  apparatus  with  perforated 
sides  cannot  be  used  for  this  purpose,  because  the 
paste  of  the  white  lead  soon  clogs  up  the  cloth  spread 
inside  of  the  drum,  and  the  water  cannot  be  forced 
out.  It  has  therefore  been  thought  more  advan- 
tageous to  separate  the  water  from  the  white  lead  by 
means  of  the  difference  in  their  specific  gravities, 
according  to  the  law  that  the  centrifugal  power  of  a 
body  is  proportional  to  its  increase  of  specific  gravity. 
After  having  tried  a  revolving  drum  without  holes  on 
its  sides,  it  was  found  that  the  thin  paste  of  the  white 
lead  was  not  following  the  same  rapid  motion  of  the 
drum,  and  that  by  bringing  the  apparatus  to  a  rest,  the 
water  was  diluting  the  white  lead  again.  In  order  to 
obviate  this  inconvenience,  radial  partitions  were  put 
inside  of  the  drum,  and  these  carrying  the  liquid  with 
them,  a  complete  separation  took  place  in  ten  minutes. 
The  white  lead,  as  a  thick  paste,  lies  against  the  sides 
of  the  drum,  and  the  clear  water  is  on  the  top  of  it 
and  may  easily  be  decanted.  The  white  lead  is  then 
put  into  pots,  and  dried  first  at  the  ordinary  tempera- 
ture, and  afterwards  in  a  stove. 

The  white  lead  prepared  by  this  process  remains 
wet  until  it  is  packed,  and  there  is  no  danger  of  its 
dust  being  inhaled  by  the  workmen.  Nearly  all  the 
work  is  done  by  machinery. 

Observed  under  the  microscope,  this  white  lead 
shows  no  angular  or  translucent  parts;  it  is  formed 
of  exceedingly  small  spheres,  scarcely  as  large  as 
those  obtained  by  the  Holland  process.   These  spheres 


102 


MANUFACTUKE  OF  COLORS. 


are  entirely  opaque,  and  this  quality,  with  their  fine- 
ness, explains  their  great  body  or  covering  power. 

The  composition  of  this  w^iite  lead,  in  the  various 
stages  of  its  manufacture,  is  determined  by  decom- 
posing a  sample  of  it,  dried  at  120°  C.  with  nitric  acid 
in  the  Geisler  apparatus  for  determining  by  loss  the 
carbonic  acid.  Another  portion  of  the  dried  substance 
is  melted  in  a  covered  porcelain  crucible,  so  as  to 
ascertain  by  loss  the  carbonic  acid  and  water.  After 
deducting  the  carbonic  acid  of  the  first  test,  the 
difierence  or  water  allows  of  the  calculation  of  the 
hydrated  protoxide  of  lead.  On  the  other  hand,  the 
proportion  of  carbonate  of  lead  is  calculated  from  that 
of  carbonic  acid. 

An  analysis  of  the  white  lead  manufactured  by  this 
process  gave : — 

PbO  86.34 

CO^  11.34 

HO        ........  2.32 


And,  as  the  calculated  composition  of  the  formula 


we  see  that  the  manufactured  product  contains  a 
slight  excess  (0.12  per  cent.)  of  neutral  carbonate  of 
lead. 

In  the  Benson  process,  modified  by  Mr.  Wollner, 
finely  pulverized  litharge  is  introduced  into  a  long 
horizontal  wooden  cylinder,  with  about  1  per  cent,  of 
neutral  acetate  of  lead,  and  sufiicient  water  to  make 
a  thin  paste.    The  apparatus  revolves  slowly,  and  a 


100.00 


2(PbO.CO0  +  PbO.HO,  is 


PbO 
CO^ 
HO 


86.3t 
11.32 
2.31 


WHITE  COLOKS. 


103 


continuous  stream  of  carbouic  acid  gas,  obtained  by 
the  combustion  of  coke,  is  introduced  through  the 
hollow  axis.  In  order  to  absorb  this  gas  as  thoroughly 
as  possible,  it  is  made  to  pass  through  several  similar 
cylinders  connected  together.  The  evaporated  water 
is  replaced  and  the  paste  kept  in  a  semi-fluid  state. 
After  a  few  days  all  the  litharge  is  transformed  into 
white  lead,  which  is  ground  in  two  consecutive  mills, 
and  compressed  and  dried. 

Mr.  Griineberg  has  still  modified  this  process  by 
adding  to  the  litharge  about  50  per  cent,  in  weight  of 
granulated  lead.  The  latter  not  only  reduces  to  a 
great  degree  of  comminution  the  white  lead  formed, 
but  also  causes  by  its  oxidation  an  elevation  of 
temperature  which  aids  the  operation  considerably, 
since  the  litharge  is  transformed  into  white  lead  in 
half  the  time  previously  necessary.  This  white  lead 
does  not  require  any  further  grinding,  being  already 
finer  than  the  ordinary  ground  white  lead,  and  having 
great  body. 

It  has  often  been  observed  that  in  this  process  or 
that  of  Mr.  Benson,  the  ordinary  commercial  litharge 
is  not  sufficiently  pure,  being  often  contaminated 
with  the  oxides  of  copper  and  iron.  The  oxide  of 
copper  imparts  to  the  white  lead  mixed  with  oil,  the 
property  of  soon  becoming  yellow  in  contact  with  the 
air;  and  this  is  explained  from  the  reduction  of  the 
copper  oxide  by  the  essence  of  turpentine  mixed  with 
the  paint.  For  instance,  a  sample  of  white  lead, 
strongly  impregnated  with  oxide  of  copper,  was 
ground  with  linseed  oil  and  turpentine,  and  spread 
upon  a  pane  of  glass  which  was  then  exposed  to  the 
air  and  the  light.  After  a  few  days  the  coat  had 
become  yellow,  and,  being  scraped,  was  treated  with 


104 


MANUFACTURE  OF  COLORS. 


ether  in  order  to  dissolve  the  oil.  The  residue  was 
then  dissolved  in  hydrochloric  acid,  filtered  rapidly, 
and  the  filtrate  treated  with  ammonia.  The  liquor 
was  colorless  at  the  beginning,  but  became  blue  by 
degrees  from  the  top.  This  proves  the  presence  of 
the  oxide  of  copper.  Another  sample  of  the  same 
white  lead  was  also  ground  with  pure  linseed  oil, 
without  turpentine,  and  spread  upon  a  pane  of  glass. 
After  exposure  to  the  light  and  the  air  the  coat  re- 
mained white,  which  proves  that  the  yellow  discolora- 
tion was  due  to  the  essence  of  turpentine. 

A  fine  commercial  white  lead  requires,  therefore, 
that  the  litharge  be  fi'ee  from  copper.  The  finely 
powdered  oxide  of  lead  may  be  treated  with  a  solution 
of  carbonate  of  ammonia  until  the  liquors  are  no 
longer  colored  blue.  But,  as  this  operation  is  slow 
and  somewhat  costly,  it  is  preferable  to  transform 
into  litharge  a  pure  metallic  lead,  and  the  white  lead 
will  not  then  become  yellow. 

We  may  add  a  few  observations  on  the  chemical 
states  in  which  oxide  of  copper  impairs  the  colors  of 
white  lead  paints,  or,  on  the  other  hand,  does  not 
injure  them  sensibly.  It  has  been  observed  that, 
when  the  liquors  holding  copper  were  precipitated  by 
carbonate  of  soda,  the  paint  remained  perfectly  white. 
This  fact  is  easily  explained  theoretically,  since  the 
carbonate  of  copper  is  not,  like  the  oxide,  reduced  by 
the  essence  of  turpentine.  As  a  proof,  the  following 
experiments  were  made : — 

I.  500  grammes  of  Goslaer  litharge  were  trans- 
formed into  white  lead  by  the  Benson  process,  with 
a  solution  of  neutral  acetate  of  lead  and  a  stream  of 
carbonic  acid.  The  product  was  well  washed  and 
dried. 


WHITE  COLORS. 


105 


II.  An  equal  quantity  of  the  same  litharge  was 
very  finely  powdered,  and  treated  with  a  solution  of 
carbonate  of  ammonia  until  fresh  liquors  were  no 
longer  colored  blue.  This  litharge  was  then  trans- 
formed into  white  lead,  like  the  former  sample. 

III.  500  grammes  of  the  same  litharge  were  dis- 
solved, without  previous  purification,  in  the  shape  of 
a  solution  of  subacetate  of  lead,  which,  after  fitration, 
was  completely  precipitated  by  carbonate  of  soda. 
The  product  was  well  washed  and  dried. 

The  white  leads  obtained  by  these  three  methods 
were  ground  in  linseed  oil  and  essence  of  turpentine, 
and  coats  laid  over  equal  surfaces. 

l^o.  I.  began  to  turn  yellow  after  twenty-four 
hours.  'No,  II.  remained  perfectly  white.  No,  III., 
which  had  as  much  copper  as  No,  L,  but  in  the  car- 
bonate state,  was  not  discolored. 

It  results  from  these  experiments  that,  in  general, 
copper  in  white  lead  may  be  the  cause  of  its  turning 
yellow,  when  the  metal  exists  in  the  form  of  oxide 
(CuO),  but  not  in  that  of  carbonate. 

8th.  MuUin^s  Process. 

The  improvements  claimed  in  the  patent  of  Mr. 
MuUin  are:  Mrst,  A  process  for  the  separation  of 
metallic  oxides  from  the  fused  metals,  by  forcing 
gases  or  atmospheric  air  through  the  metallic  mass 
by  means  of  a  compressing  apparatus.  There  are 
also  the  means  of  removing  the  alloys,  or  the  oxides 
from  the  surface  of  the  bath.  Second,  A  process  for 
the  manufacture  of  white  lead  by  submitting  the 
oxides  to  the  fumes  of  vinegar  and  to  carbonic  acid. 
Third,  The  employment  of  magnets  for  separating 
the  iron  from  the  metals  with  which  it  is  mixed. 


lOG 


MANUFACTURE  OF  COLORS. 


I.  The  apparatus  for  melting  the  metals  and  sepa- 
rating the  oxides  (Fig.  3)  is  composed  of  a  furnace 
A  A,  supporting  a  kettle  or  boiler  b  c,  which  is  heated 
by  the  fireplace  d.    A  tube  a  terminated  by  a  ball 


Fig.  3. 


hollow  and  with  longitudinal  slits,  is  immersed  in  b, 
and  communicates  in  an  upper  story  with  a  holder  c 
(Fig.  4),  in  which  a  pump  d  compresses  the  gas  or 
air,  or  their  mixture,  which  passes  through  the  fused 
metal  and  oxidizes  it.  The  flow  of  gas  or  air  is  regu- 
lated by  the  valve  e. 

The  oxide  is  removed  by  the  revolving  rake  f,  the 
endless  chain  of  which  is  carried  by  two  pulleys  hh. 
The  tension  is  regulated  by  the  screws  ff^  and  the 
oxide  passes  upon  the  inclined  spout  J,  which  is 
made  of  iron  rods  sufficiently  close  to  retain  the  oxide, 
and  hot  enough  to  melt  the  non-oxidized  metal,  and 
return  it  to  the  bath.    The  oxide  frills  into  the  box  K. 

The  tube  a  may  raised  or  lowered  by  means  of  the 
counterweight  h  and  the  flexible  tube  g.    Two  safety 


WHITE  COLORS. 


107 


valves  ij  are  placed,  the  one  upon  the  pipe  Z*,  and  the 
other  upon  the  holder  c.  To  the  latter  is  also  added 
a  gauge  I  to  indicate  the  pressure,  which  should  be 
sufficiently  energetic  to  overcome  the  column  of 


Fig.  4. 


molten  metal,  and  to  maintain  a  constant  flow  of  gas. 
Another  pipe  m  connects  the  pump  d  with  a  gas 
holder,  when  gas,  instead  of  atmospheric  air,  is 
employed.  In  the  case  of  air,  the  pipe  m  is  dis- 
connected at  n.  The  piston  of  the  pump  d  is  set  in 
motion  by  the  side  rod  o,  attached  to  the  crank  p 
which  is  fixed  on  the  same  axis  as  the  pulley  q. 

Fig.  5  shows  the  disposition  which  prevents  the 
admixture  of  the  metal  with  the  oxide.  The  inclined 
metallic  plate  a,  of  iron  or  other  metal,  is  attached  to 
the  pipe  b,  a  little  above  the  perforated  ball  c.  The 
current  of  air  is  conducted  by  a  up  to  the  edge  F  of 
the  kettle,  and  there  is  no  agitation  on  the  surface  of 
the  bath,  where  the  oxidation  takes  place. 


108  MANUFACTURE  OF  COLORS. 

Fig.  6  explains  another  mode  of  oxidizing  metals. 
Black  oxide  of  manganese  is  put  into  the  iron  pot  A, 


Fig.  5.  Fig.  6. 


having  holes  at  b  and  D,  and  a  handle  s.  When  this 
pot  is  immersed  in  the  bath,  the  metal  penetrates 
through  B,  and  heats  the  manganese,  which  disen- 
gages oxygen  and  rapidly  oxidizes  the  metal. 

If  the  metal  employed  be  lead  holding  silver,  the 
latter,  not  being  oxidized,  goes  down  to  the  bottom  of 
the  kettle,  from  which  it  is  removed  through  the  plug 
N  (Fig.  7),  of  the  pipe  mo,  which  is  kept  hot  by  a 
fire  at  R. 


Fig.  7. 


II.  The  oxide  of  lead  obtained  by  any  one  of  these 
processes  is  ground,  sifted,  and  washed,  and  then  put 


WHITE  COLORS. 


109 


into  the  trays  t  t  (Fig.  8),  which  are  lined  with  lead 
and  hermetically  closed 
with  covers.  These  trays 
are  placed  in  a  lead  box, 
and  the  room  is  kept  at  a 
temperature  of  from  38°  to 
48°  C.  The  1  ayers  of  oxide 
of  lead  are  about  3  centi- 
metres thick,  and  are  kept 
wet  with  water.  When 
the  apparatus  is  filled  with  the  litharge,  then  begins 
the  introduction  of  the  fumes  of  vinegar  distilled  in 
an  ordinary  still,  and  of  carbonic  acid  kept  in  a  gas 
holder  in  an  adjoining  room.  Before  removing  the 
covers  of  the  trays,  the  stopcocks  in  the  pipes  through 
which  the  vinegar  vapors  and  the  carbonic  acid  j^ass 
are  turned  oflP.  By  these  means,  when  the  proper 
temperature  has  been  maintained,  the  oxid^  of  lead  is 
transformed  into  carbonate. 

Another  method  of  manufacturing  white  lead, 
proposed  by  the  same  inventor,  consists  of  a  series  of 
large  stoneware  jars  a  (Fig.  9),  in  which  are  suspended, 
by  woollen  or  cotton  cords,  several  sponges  which 
do  not  touch  the  sides  of  the  jars. 
By  capillary  attraction,  a  solution  Fig.  9. 

of  neutral  acetate  of  lead  held  in 
X  keeps  the  sponges  wet.  The 
salts  of  lead  are  transformed  into 
carbonates  by  a  current  of  carbonic 
acid  which  passes  through  the  jars. 
The  sponges  are  then  removed, 
and  washed  in  pure  water.  After 
settling,  the  clear  liquors  are  de- 
canted for  a  future  operation. 


110 


MANUFACTURE  OF  COLORS. 


III.  Should  the  metallic  oxides  contain  iron,  this 
is  removed  in  the  following  manner  :  A  wooden  table 
or  trough  y  (Figs.  10  and  11)  is  furnished  with  a 
certain  number  of  magnets     the  poles  of  which  pass 

Fig.  10.  Fig.  11. 


through  the  bottom  of  the  table.  The  latter  is  inclined 
30°  and  has  a  slow  oscillating  motion.  The  oxide  is 
delivered  by  the  hopper  a,  and  the  iron  is  arrested  by 
the  magnets. 

9th.  Schuzenbach  Process. 

Carbonate  of  lead  may  be  produced  by  a  great  many 
chemical  decompositions,  but  the  product  is  not  white 
lead.  Nevertheless  the  inventors  are  not  to  be  dis- 
couraged, and  have  tried  many  ways  of  arriving  at 
results  more  or  less  satisfactory.  There  are  a  great 
many  processes  described,  some  of  which  show  great 
ingenuity.  On  that  account,  and  in  order  to  give 
some  idea  of  what  has  been  done  in  that  direction, 
we  shall  examine  several  of  these  methods. 

The  principal  inconvenience  of  the  ordinary  pro- 
cesses for  the  manufacture  of  white  lead,  is  that  they 
are  unhealthy.     The  method  proposed  by  Mr.  S. 


WHITE  COLORS. 


Ill 


Bchnzenbach,  of  Friburg,  seems  to  be  entirely  whole- 
some. It  is  also  said  to  require  less  capital,  and  less 
room,  and  to  give  a  larger  product. 

In  a  room  so  arranged  as  to  be  heated  from  40°  to 
60°  C,  several  wooden  tubs  are  placed  close  to  each 
other.  These  tubs  are  filled  with  alternate  layers  of 
shavings  impregnated  with  vinegar,  and  lead  plates 
or  buckles,  each  layer  being  separated  by  perforated 
wooden  partitions  which  can  be  easily  removed,  and 
allow  of  the  free  circulation  of  gases  and  vapors.  The 
tubs  are  then  closed  with  wooden  covers,  and  kept  at 
the  proper  temperature  until  the  shavings  have  become 
dry.  The  lead  buckles,  which  are  almost  entirely 
corroded,  are  then  removed  and  deprived  of  the 
adhering  white  lead  by  being  placed  in  water.  The 
shavings  being  moistened  with  vinegar,  the  operation 
may  be  begun  anew. 

The  white  lead  thus  produced  should  always  be 
washed  with  pure  water  in  order  that  the  various 
acetates  of  lead,  copper,  or  iron,  be  dissolved  and 
separated  from  the  insoluble  carbonate.  After  several 
washings,  the  product  is  dried. 

The  first  waters  employed  for  washing,  may  be 
decanted  for  saving  the  acetates  of  lead  or  copper  still 
held  in  them. 

loth.  Sewell  Process. 

This  process  comprises  four  distinct  operations: 
jFii'st,  an  improved  method  of  making  oxide  of  lead; 
Second,  the  production  of  a  white  lead  of  superior 
quality,  which  contains  less  carbonic  acid  than  the 
average  commercial  white  lead ;  Third,  the  employ- 
ment of  carbonic  acid  produced  by  other  means  than 
by  combustion  in  the  air ;  Fourth,  a  mode  of  washing 


112 


MA^^UFACTURE  OF  COLORS. 


the  white  lead,  by  which  the  foreign  substances  are 
removed. 

I.  The  incompletely  oxidized  lead,  that  is,  that 
mixed  with  a  certain  proportion  of  metallic  lead  and 
red  lead,  is  kept  at  a  red  heat  in  a  reverberatory  fur- 
nace for  three  or  four  hours,  and  stirred  all  the  time. 
When  the  whole  has  become  transformed  into  pro- 
toxide of  lead,  it  is  immediately  thrown  into  a  closed 
vessel  to  prevent  further  oxidization  by  contact  with 
the  air. 

II.  During  the  second  operation,  the  solution  of 
oxide  of  lead  is  precipitated  either  by  an  alkali  com- 
bined with  a  certain  proportion  of  carbonic  acid,  or 
by  carbonic  acid  alone.  In  the  first  case,  the  oxide 
of  lead  is  dissolved  in  weak  nitric  or  acetic  acid,  and 
to  the  solution  is  added  potassa,  soda,  or  ammonia, 
in  quantity  sufficient  to  neutralize  the  acid.  When 
carbonic  acid  is  used,  the  solution  of  acetate  of  lead 
is  stirred  all  the  time  that  the  gas  is  passing  through 
it.  As  soon  as  the  solution  acquires  an  acid  reaction 
the  flow  of  carbonic  acid  is  stopped. 

III.  The  carbonic  acid  may  be  obtained  by  mixing 
one  part  of  coke  dust  with  seven  parts  of  finely  pul- 
verized sulphate  of  lime,  or  ten  of  sulphate  of  baryta, 
or  eight  parts  of  sulphate  of  strontia.  These  various 
mixtures  are  kept  at  a  cherry-red  heat  in  an  ordinary 
gas  retort  as  long  as  carbonic  acid  is  produced, 
which,  after  cooling  over  the  water  of  the  main  pipe, 
goes  to  a  gas  holder  before  being  used  in  the  manu- 
facture of  white  lead. 

Another  method  of  generating  carbonic  acid  gas 
consists  in  passing  steam  through  a  clay  retort  filled 
with  finely  broken  coke  and  kept  at  a  cherry-red  heat. 
The  steam  is  decomposed,  and  carbonic  acid  and  other 
gases  are  produced  and  collected  in  a  gas  holder. 


WHITE  COLORS. 


113 


IV.  The  white  lead  is  washed  under  pneumatic 
and  hydrostatic  pressure,  in  order  to  remove  the  acid 
and  other  substances  before  it  is  dried. 

Explanation  of  the  Apparatus, — Fig.  12  is  a  trans- 
verse section  of  a  cast-iron  receiver  a  a  lined  with 
copper,  in  order  to  prevent  the  contact  of  the  white 
lead  with  the  iron.  5,  cover  held  by  screws,  c,  space 
occupied  by  the  white  lead  which  is  to  be  washed. 

Fig.  18  is  a  section  of  the  inverted  receiver  with 
its  cover  on. 

Fig.  13.  Fig.  14. 


Fig.  14  is  a  longitudinal  section  of  the  same 
receiver,  held  in  a  wooden  frame. 

Fig.  15  is  another  longitudinal  section,  but  in  an 
inverted  position,  which  'is  that  of  the  apparatus 
during  the  operation.  The  groove  at  is  packed 
tight  with  tow  when  the  cover  is  on.  A  thick  brass 
plate  e  e  (Figs.  16  and  17),  perforated  with  holes,  is 
attached  to  the  cover.  The  holes  are  slantinof  near 
the  cover,  and  this  disposition  allows  of  a  communi- 
cation between  themselves,  and  a  narrow  passage 
between  the  plate  and  the  cover.  The  copper  tubes 
ff  fast  in  the  cover,  communicate  with  the  narrow 
8 


114 


MANUFACTURE  OF  COLORS. 


passage  back  of  the  plate  e  e,  and  carry  the  water 
which  passes  through  the  holes  of  the  plate  during 
the  washing  of  the  white  lead. 

Fig.  15. 

Fig.  17. 


Fig.  16. 


The  receiver  a  is  supported  on  the  frame  by  two 
hollow  trunnions  A,  lined  with  copper,  g  is  closed 
with  a  plug  during  the  operation,  and  li  carries  the 
tube  which  delivers  the  water  brought  by  the  tube 
Z.  m  is  the  connectino^  stuffinof-box.  After  the  re- 
ceiver  is  filled  with  white  lead  the  cover  is  put  on, 
and  the  apparatus  is  turned  upside  down  by  means  of 
pinion  and  wheel  gear. 

A  puinp  injects  the  water  through  I  and  Ic  upon  the 
surface  of  the  white  lead,  and  forces  it  through  that 
substance  and  a  filtering  cloth  o,  spread  upon  the 
plate  6.  The  water  escapes  from  the  holes  of  the 
plate  into  the  narrow  passage  behind,  and  finally 
through  the  tubes  ff.  The  washing  should  be  con- 
tinued until  the  water  remains  perfectly  clear. 

During  this  operation  the  white  lead  has  been 
strongly  compressed  against  the  cover  of  the  appa- 
ratus, and  the  water  remaining  above  is  run  out 
through  the  plug  hole  g.    The  apparatus  is  then 


WHITE  COLOKS. 


115 


brought  to  its  former  position,  the  cover  raised  by 
means  of  the  screw  jp,  and  the  white  lead  removed. 

11th.  Crompton  Process. 
This  process  consists — 

First  In  purifying  the  gases  obtained  from  bitu- 
minous coal  burned  by  atmospheric  air  introduced  in 
a  peculiar  manner; 

Second,  In  washing  the  white  lead  in  a  solution  of 
carbonate  of  soda,  or  any  analogous  chemical  prepa- 
ration, the  proportions  of  which  are  indicated  fur- 
ther on ; 

Third.  In  employing  a  basic  nitrate  of  lead  for  the 
production  of  carbonate  of  lead; 

Fourth.  In  using  litharge,  massicot,  or  any  protoxide 
of  lead,  boiled  with  nitric  acid  or  nitrate  of  lead,  and 
exposing  the  hot  solution  to  the  action  of  carbonic 
acid ; 

Fifth.  In  condensing  and  purifying  the  carbonate 
of  lead  thus  obtained  by  a  simple,  new,  and  economi- 
cal method. 

For  these  various  operations  we  need:  1.  A  special 
apparatus  for  the  production  of  white  lead  by  means 
of  litharge,  massicot,  or  protoxide  of  lead,  and  this 
apparatus  is  provided  with  a  pair  of  forge  bellows,  a 
safety  valve,  and  other  accessories ;  2.  A  cylindrical 
cast-iron  furnace  with  a  cover  of  the  same  material, 
which  is  held  by  a  screw  and  luted  with  clay,in  order 
to  prevent  the  access  of  the  air;  3.  A  large  cylindri- 
cal wrought-iron  vessel  which  can  be  hermetically 
closed,  and  which  contains  a  diaphragm  of  metallic 
gauze  and  a  stirrer.  The  air  or  gases  circulate 
through  a  conduit  of  a  spiral  form,  and  escape  above 
by  a  central  opening ;  4.  A  copper  pump  for  removing 


WHITE  COLORS. 


117 


the  liquors  from  the  various  receivers,  and  forcing  them 
upon  cloth  sieves  disposed  on  top  of  other  tanks ;  5. 
Lastly,  the  other  vessels,  pipes,  stopcocks,  and  acces- 
sories necessary  for  obtaining  the  gases,  washing,  and 
separating  the  carbonate  of  lead. 

The  following  figures  will  explain  the  apparatus : 
In  Fig.  18  A  represents  the  bellows;  b,  the  rod  for 
operating  it;  c,  a  weight  necessary  to  overcome  the 
resistance  of  the  air  introduced  into  the  furnace;  d, 
safety  valve,  and  e  the  tuyere. 

F  is  the  furnace  composed  of  a  cast-iron  cylinder, 
stout  enough  for  the  purpose ;  a',  cast-iron  cover  which 
may  be  removed  at  will ;  h\  clamp  fastened  to  the 
edge  of  the  furnace,  and  through  which  passes  the 
screw  d  which  compresses  the  cover  against  the  clay 
luting  put  between  it  and  the  cylinder. 

The  flame  passes  through  the  cast-iron  pipe  g  into 
the  cast-iron  cylinder  h  i,  called  the  flame  receiver. 

K  is  a  double-elbow  pipe  starting  from  the  top  of 
H  I,  which  can  he  cleaned  of  ashes  and  dust  through 
movable  covers  fixed  on  the  top  and  bottom. 

M  is  a  branch  pipe  fixed  at  o  on  the  tuyere  e,  and 
which,  without  passing  through  the  furnace,  carries 
the  blast  to  the  lower  part  of  the  flame  receiver  h  i. 

Fig.  19  shows  the  shape  and  direction  of  the  pipe 
M,  and  the  same  letters  answer  for  the  cori-esponding 
parts  of  the  previous  figure.  At  N  and  o  are  stop- 
cocks, the  former  on  the  tuyere  and  the  latter  on  the 
pipe  M,  which  has  an  area  of  one-fifth  of  that  of  the 
tuyere. 

p  is  a  large  w rough t-ir on  cylinder  called  the  washer^ 
which  is  tightly  closed,  and  through  which  pass  the 
gases  of  combustion,  q  r  is  a  disk  carrying  under- 
neath it  a  spiral  T  T  made  of  thin  sheet  iron,  and  com- 


118 


MANUFACTURE  OF  COLORS. 


municating  at  r  with  the  pipe  K  which  delivei's  the 
hot  gases.    After  circulating  through  the  spiral,  the 


Fig.  19. 


gases  escape  through  an  opening  in  the  centre  of  the 
plate  Q  R,  and  thence  rise  to  the  upper  part  of  p. 
Fig.  20  is  a  horizontal  section  of  the  spiral  t  t. 


Fig.  20. 


The  central  opening  through  which  the  cooled  and 
washed  gases  escape  is  shown  at  s. 

u  is  a  diaphragm  of  close  metallic  gauze,  which  is 
spread  upon  a  perforated  copper  plate,  and  forms  a 
complete  separation  between  the  upper  and  the  lower 
part  of  p.  V,  w,  stopcocks,  and  x  funnel  with  a  stop- 
cock. Y  vertical  shaft  of  the  stirrer  passing  through 
the  stufBng-boxes  z. 

The  hot  gases,  after  circulating  through  the  spiral 


WHITE  COLOKS. 


119 


T  T,  escape  at  S,  and  traversing  the  diaphragm  u,  pass 
out  at  a, 

5,  c  are  copper  receivers  fitted  with  copper  jackets 
d  d,  which  leave  between  them  the  spaces  e  e  for  the 
circulation  of  the  steam.  /,  pipe  conducting  the  steam 
into  those  spaces,  pipe  for  the  escape  of  the 
condensed  steam.    Jih,  stopcocks  for  removing  air. 

The  receiver  c  contains  white  lead,  and  h  holds 
litharge. 

i  (Fig.  21)  is  a  copper  pipe  forming  a  spiral  at  the 
bottom  of  the  receiver  c.    One  end  of  the  coil  is 


F'lcr,  21. 


closed  and  the  other  is  connected  with  the  pipe  a.  It 
is  perforated  with  a  quantity  of  small  holes  which 
allow  of  the  escape  of  the  hot  gases. 

]c  is  the  horizontal  arm  of  a  stirrer  placed  in  the 
vessel  h  holding  litharge. 

Z,  m,  are  copper  pumps  extracting  the  liquors  from 

c,  through  the  pipes  o,  n  dipping  into  the  apparatus. 
The  liquors  are  then  discharged  through  the  pipes  p, 

into  the  receivers  r,  8,  after  having  traversed  the 
cloth  sieves  placed  on  top,  and  spread  upon  the 
wooden  frames  t  t 

Mode  ofworhiiig  the  Apparatus. — The  cover  of  the 
furnace  f  is  removed,  and  some  burning  charcoal  is 
thrown  in.  The  stopcock  n  of  the  tuyere  is  then 
opened,  that  at  o  remaining  closed,  and  the  blast  is 


120 


MANUFACTURE  OF  COLORS. 


applied.  After  a  while  the  furnace  is  charged  with 
bituminous  coal  of  the  best  quality. 

When  the  fire  is  well  lighted,  the  cover  is  luted 
down  and  fastened  with  the  screw  c',  and  the  stopcock 
at  o  is  opened  in  order  to  complete  the  combustion 
of  the  fuel  near  the  tuyere,  before  the  gases  are 
allowed  to  escape.  In  this  manner  the  volatile  por- 
tions from  the  fuel  above  the  tuyere  are  foi'ced  to 
pass  through  the  flame,  where  they  are  burned  and 
decomposed  before  reaching  the  receiver  H  i. 

The  gases  on  arriving  in  this  receiver  are  at  a  very 
high  temperature,  and  find  themselves  brought  in 
contact  with  another  volume  of  air  forced  through 
the  pipe  m.  This  quantity  of  air  is  in  such  a  ratio 
to  that  passing  through  the  furnace,  that  the  whole 
of  the  sulphuretted  hydrogen  is  transformed  into 
sulphurous  acid  and  aqueous  vapors.  On  the  other 
hand,  the  carbonic  oxide  is  converted  into  carbonic 
acid,  and  any  combination  of  carbon  and  hydrogen 
becomes  carbonic  acid  and  water. 

We  should  avoid  passing  through  m  more  air  than 
is  needed,  otherwise  the  temperature  in  h  i  will  be- 
come lowered  so  much,  that  the  decompositon  of  the 
sulphuretted  hydrogen  and  of  the  hydrocarbons  will 
no  longer  take  place. 

The  blast  being  well  regulated,  we  throw  into  the 
washer  p  five  kilogrammes  of  carbonate  of  soda  and 
the  same  w^eight  of  carbonate  of  lead,  and  through 
the  funnel  x  we  pour  enough  water  to  cover  the  plate 
Q  R  to  the  level  of  the  stopcock  v. 

The  receivers  c,  are  then  almost  entirely  filled 
with  distilled  water.  In  h  we  put  twenty-five  kilo- 
grammes of  litharge  and  ten  of  nitrate  of  lead,  or  any 
othei"  quantity,  provided,  however,  that  this  quantity 


WHITE  COLORS. 


121 


of  nitrate  be  3^  of  the  weight  of  water  held  in  the 
receiver. 

Steam  is  admitted  into  the  spaces  e  e  of  the  jackets, 
until  the  contents  of  the  vessel  are  boiling,  and  the 
stirrer  h  is  made  to  revolve. 

The  rods  of  the  plungers  of  the  pumps  Z,  m,  are 
fixed  upon  a  common  axis  which  makes  thirteen 
revolutions  per  minute.  The  pump  m  extracts  the 
liquors  from  and  delivers  them  to  the  filtering 
apparatus  s,  from  which  they  flow  into  c;  the  other 
pump  I  takes  the  liquors  fi'om  c  with  more  or  less 
suspended  white  lead,  and  after  filtration  at  r,  lets 
them  fall  into  h. 

Thus  the  air  forced  by  the  bellows  passes  through 
the  furnace,  and  the  hot  gases  of  combustion  pass  into 
H  I,  thence  by  the  pipe  k  through  the  washer  p,  thence 
again  by  a  through  the  coil  i,  from  which  they  escape 
in  a  multitude  of  bubbles  into  the  receiver  c. 

By  the  succession  of  these  various  operations  the 
white  lead  mixed  with  the  liquors  of  c,  is  carried  to 
the  filter  r  upon  w^hich  it  is  collected.  The  liquors  h 
pass  through  the  filter  8,  upon  which  they  leave  a 
certain  proportion  of  undissolved  litharge. 

When  the  filters  ?*,  s,  are  entirely  filled  with  white 
lead  and  litharge,  they  are  removed  and  replaced  by 
new  ones. 

With  a  furnace  in  constant  operation,  the  charges 
are  renewed  every  eight  hours. 

The  stirrer  in  the  washer  p  has  a  very  slow  motion, 
and  the  litharge  in  h  should  not  be  in  such  quantity 
as  to  prevent  the  free  running  of  the  stirrer  Jc.  • 

The  water  in  p  is  always  maintained  at  the  level  of 
V,  and  the  dirty  liquors  from  time  to  time  removed 
at  w,  are  replaced  by  fresh  ones. 


122  MANUFACTURE  OF  COLORS. 

The  liquors  of  h  and  c  should  occasionally  be  tried, 
in  order  to  see  whether  any  leakage  takes  place,  or  if 
they  remain  of  a  proper  strength.  If  a  sample  of 
boiling  liquor  from  h  does  not  give  on  cooling,  a  pre- 
cipitate of  nitrate  of  lead,  this  substance  is  in  insuffi- 
cient proportion  and  more  should  be  added. 

After  having  described  the  apparatus  and  the 
various  operations  by  which  carbonate  of  lead  is  pro- 
duced, it  is  now  desirable  to  explain  the  processes 
of  Mr.  Crompton  by  which  this  substance  is  put  into 
commercial  shape,  and  the  nitrate  of  lead  mixed  with 
the  carbonate  on  the  filter,  recovered. 

To  the  former  apparatus  already  described,  we 
add :  1.  A  square  box  b  (Fig.  22),  the  bottom  of 
which  is  formed  of  a  close  canvas  filter  x;  2.  A  large 
tub;  3.  Another  tub  holding  a  vertical  bronze  shaft, 
provided  with  a  series  of  blades 

Fig.^2.           slightly  inclined,  so  as  to  divide  the 

mass  of  carbonate  of  lead  and  com- 
press it  at  the  same  time  towards 
the  bottom. 

The  substance  on  the  filter  r  is 
placed  in  the  box  up  to  the  level  c, 
and  fresh  water  is  poured  upon  it  to 
dissolve  the  nitrate  of  lead.  The 
washing  is  continued  until  a  sample 
of  the  filtered  liquor  ceases  to  be- 
come white  by  the  addition  of  a  solution  of  carbonate 
of  soda. 

All  the  washings  are  collected  underneath  in  the 
tub  D,  and  are  afterwards  used  in  the  litharge  receiver 
h.    In  this  manner  all  the  nitrate  of  lead  is  saved. 

The  washed  white  lead  from  the  box  b  is  thrown 
into  the  tub  e  (Figs.  23  and  2^)  holding  the  bronze 


WHITE  COLORS. 


123 


shaft  F  with  its  inclined  blades  g  g.  By  the  motion 
of  the  stirrer  the  mass  of  carbonate  of  lead  is  made 
thoroughly  homogeneous,  and  the  separated  water 
passes  into  the  false  bottom  h  through  a  cloth  spread 
upon  the  perforated  partition. 


The  water  is  removed  by  the  stopcock  l,  and  the 
carbonate  of  lead  is  conducted  by  the  inclined  gutter 
K  into  the  hopper  l',  from  which  it  is  ground  between 
the  stones  z  z,  to  fall  into  the  tub  m.  Lastly,  it  is 
formed  into  lumps  and  dried. 

To  sum  up,  Mr.  Crompton  claims  the  following 
points  as  new : — 

I.  The  employment  of  carbonic  acid  and  gases 
produced  by  bituminous  coal,  which  is  burned  in  such 
a  manner,  by  a  peculiar  introduction  of  air,  that  th^ 
vapors  which  otherwise  might  injure  the  quality  of 
the  product  are  destroyed. 

II.  The  manufacture  of  white  lead  by  a  mixture  of 
nitric  acid  and  oxide  of  lead,  in  such  proportions  that 


124 


MANUFACTUllE  OF  COLORS. 


there  be  an  excess  of  oxide ;  or  by  keeping  at  the 
point  of  ebullition  a  mixture  of  litharge,  massicot,  or 
any  oxide  of  lead,  with  a  solution  of  commercial  nitrate 
of  lead.  A  pure  carbonate  of  lead  is  obtained  by 
passing  a  stream  of  carbonic  acid  through  these  hot 
solutions. 

III.  The  constant  recovery  of  the  nitric  acid  or 
nitrate  of  lead  employed,  serving  for  fresh  additions 
of  litharge. 

IV.  The  purification  of  the  carbonate  of  lead  by 
successive  washings,  which  were  not  practised  before 
the  above  process  was  invented. 

Mr.  Crompton,  since  his  patent  of  September  7th, 

1838,  has  obtained  other  certificates  of  improvements 
of  the  dates  of  February  6th  and  July  18tb,  1839. 

The  improvements  of  the  patent  of  February  6th, 

1839,  are  :— 

1.  The  employment  of  anthracite,  coke,  and  any 
other  carboniferous  substances,  instead  of  charcoal 
generally  used  for  the  pn  duction  of  carbonic  acid. 
Also,  the  purification  of  the  gases  of  the  combustion, 
and  the  destruction  of  the  vapors  which  may  injure 
the  purity  of  the  carbonate  of  lead.  This  purification 
is  done  as  follows  : — 

By  a  second  combustion  effected,  as  we  have  already 
seen,  in  a  flame  receiver  by  means  of  a  new  addition 
of  atmospheric  air.  The  combinations  of  sulphur, 
carbon,  and  hydrogen,  are  thus  transformed  into 
water  and  carbonic  and  sulphurous  acids. 

By  condensing  the  sulphurous  acid  and  the  still 
remaining  sulphuretted  hydrogen,  in  solutions  hold- 
ins^  neutralizino-  substances. 

2.  The  use  of  the  nitrate  of  lead,  instead  of  the 
acetate,  hitherto  employed. 


WHITE  COLORS. 


125 


3.  The  proper  degree  of  temperature  necessary  to 
keep  in  solution  the  basic  nitrate  of  lead,  which  is 
very  slightly  soluble  in  the  cold. 

This  improvement  is  not  limited  to  the  foregoing 
combinations:  the  mode  of  preparing  carbonic  acid 
is  equally  good  whether  we  employ  the  acetate  or 
the  nitrate  of  lead.  We  may  also  use  the  nitrate  of 
lead  in  connection  with  carbonic  acid  made  from 
charcoal,  and  produce  the  carbonate  of  lead  in  hot 
solutions,  whatever  be  the  acid  employed. 

Lastly,  the  precipitation  of  the  carbonate  of  lead  in 
hot  liquors,  has  a  great  effect  on  its  mode  of  aggre- 
gation. 

The  first  patent  indicates  hot  solutions  of  nitric  acid 
or  of  nitrate  of  lead  as  solvents,  and  the  purification 
of  the  carbonic  acid  whatever  be  the  solvent  employed. 

The  last  patent  of  July  18th,  1839,  comprises  the 
heating  of  the  lead  solutions  during  their  preparation, 
as  well  as  during  their  precipitation  by  carbonic  acid. 
The  solvent  is  acetic  acid  or  the  acetate  of  lead. 

The  temperature  should  be  about  60°  C,  or  a  little 
above.    The  solution  is  composed  as  follows: — 

Pure  acetate  of  lead  or  its  equivalents  in  oxide 

of  lead  and  acetic  aeid        ....    10  parts. 
Litharge  (oxide  of  lead)         .       .       .       .    25  " 

Water   200  " 

These  proportions  may  vary  somewhat,  however. 

12th.  Gannal  Process, 

This  process  consists: — 

1.  In  granulating  the  lead ; 

2.  In  reducing  the  granules  to  a  finer  degree  of 
comminution  by  mutual  attrition  in  a  leaden  cylinder; 


4 


126 


MAOTFACTURE  OF  COLORS. 


3.  In  oxidizing  the  metal  by  the  introduction  of  air 
into  the  apparatus ; 

4.  In  carbonating  the  oxide  with  a  mixture  of  air 
and  carbonic  acid ; 

5.  In  aiding  the  oxidation  by  an  addition  in  the 
apparatus  of  nitric  acid  or  nitrate  of  lead  ; 

6.  In  washing  the  product  thus  obtained; 

7.  In  hastening  its  desiccation  by  a  previous  pres- 
sure which  expels  most  of  the  water; 

8.  In  dividing  the  pressed  paste  into  square  blocks ; 

9.  In  drying  these  blocks  in  a  stove-room. 

This  process  has  been  improved  by  Mr.  Yersepuy, 
as  we  have  already  seen. 

13th.  Rostaing  Procei^s. 

Mr.  de  Kostaing,  in  1858,  proposed  for  the  manu- 
facture of  white  lead  and  massicot  a  process  based 
upon  the  pulverization  of  metals  submitted,  when 
melted,  to  centrifugal  action.  A  continuous  stream 
of  molten  lead  falls  upon  a  metallic  disk,  0.25  metre 
in  diameter,  making  a  maximum  of  2000  revolutions 
per  minute,  and  is  pi'ojected  with  great  force  tangen- 
tially  to  its  circumference.  Four  or  five  minutes  are 
sufiicient  to  thus  pulverize  about  100  kilogrammes 
of  lead.  The  fine  metallic  powder,  being  still  hot,  is 
rapidly  oxidized  in  its  passage  through  the  air,  and 
may  be  converted  into  massicot  or  red  lead,  or  may  be 
combined  with  carbonic  acid.  This  process  has  not 
been  put  into  practice. 

14tli.  Mulhouse  White  Lead. 

This  is  a  combination  of  sulphuric  acid  and  oxide  of 
lead,  being  the  residue  of  the  manufacture  of  acetate 
of  alumina.    It  is  thoroughly  washed  with  water, 


WHITE  COLORS. 


127 


passed  through  a  silk  sieve,  and  drained  upon  cloth 
filters.  It  is  afterwards  moulded  in  the  shape  of  a 
truncated  cone,  and  dried.  This  product,  misnamed 
white  lead,  cannot  be  used  for  oil  painting,  since  it 
has  no  body — does  not  cover.  We  mention  it  because 
it  is  frequently  employed  for  adulterating  real  white 
lead. 

This  sulphate  of  lead  may  by  transformed  into  car- 
bonate by  boiling  it  with  a  solution  of  carbonate  of 
soda  or  of  potassa.  But  this  operation  renders  it 
more  expensive  than  real  white  lead,  and  the  product 
is  still  contaminated  with  a  certain  proportion  of 
sulphate  of  lead. 

,  15th.  Silver  White  or  Light  White. 

This  white,  often  employed  for  decorating  and  for 
artistic  painting,  is  a  white  lead  of  the  first  quality 
which  has  been  peculiarly  well  washed. 

A  superior  quality  of  silver  white  for  delicate  oil 
painting  may  be  obtained  by  dissolving  500  grammes 
of  acetate  of  lead  in  2  litres  of  boilino^  water  and 
diluting  with  4  litres  more  of  water.  Then  a  solution 
of  370  grammes  of  soda  crystals  in  2  litres  of  boil- 
ing water,  is  slowly  poured  into  the  former  liquors, 
stirring  all  the  while.  The  two  mixed  solutions  are 
allowed  to  settle  for  two  hours,  when  the  supernatant 
liquid  is  decanted.  The  precipitate  is  washed  five 
or  six  times  by  decantation,  then  drained  upon  a 
cloth,  and  dried  in  the  dark  at  a  gentle  heat. 

16th.  Testing  the  Purity  of  White  Leads. 

We  should  carefully  avoid  mixing  with  white  lead 
substances  which  may  impair  its  brightness,  since  a 


i 


128 


MAXUFACTIJRE  OF  COLORS. 


pure  white  is  its  main  quality.  We  shall  see  farther 
on  what  its  composition  is. 

White  lead  should  be  kept  in  closed  vessels,  other- 
wise it  will  acquire  a  brown  shade.  It  forms  the 
basis  of  a  great  many  pigments.  It  should,  for  good 
paintings,  be  pure  and  without  admixtures  ;  however, 
house  paintei's  add  to  it  variable  proportions  of  chalk 
or  Meudon  white,  but  the  painting  is  without  con- 
sistency or  durability.  Here  is  the  process  indicated 
by  Watin  for  distinguishing  white  lead  from  chalk. 
A  hole  is  made  in  a  piece  of  charcoal,  which  is  then 
ignited  and  a  pinch  of  white  lead  thrown  in.  Air  is 
blown  upon  the  charcoal  in  order  to  keep  up  the  com- 
bustion, and  the  white  lead  first  turns  yellow,  and 
after  a  few  minutes  becomes  reduced  to  bright  glob- 
ules of  metallic  lead.  Chalk  (carbonate  of  lime),  on  the 
other  hand,  may  lose  its  carbonic  acid  by  the  opera- 
tion, but  the  lime  will  remain  as  .a  white  powder  upon 
the  charcoal. 

If  we  desire  to  ascertain  the  proportion  of  car- 
bonate of  lime  mixed  with  the  carbonate  of  lead,  we 
weigh  100  grammes  of  the  sample,  and  mix  them 
with  50  grammes  of  charcoal  powder.  The  whole 
being  smelted  in  a  crucible,  a  button  of  metallic  lead 
is  produced,  which  is  weighed.  We  then  add  24 
per  cent,  to  the  number  obtained,  and  subtracting  this 
sum  from  the  previous  100  grammes,  the  difference 
is  the  weight  of  the  carbonate  of  lime.  The  24  per 
cent,  represent  about  the  weight  of  the  carbonic  acid, 
water,  and  oxygen  separated  from  the  carbonate  of  lead. 

These  two  tests  would  be  sufficient  if  carbonate  of 
lime  were  the  only  foreign  substance  of  the  mixture. 
But  as  sulphate  of  lead  may  also  be  present,  we  are 
obliged  to  employ  tests  by  the  wet  way.    For  in- 


WHITE  COLORS.  129 

stance  we  put  25  grammes  of  the  sample  into  a  glass 
flask,  and  pour  gradually  upon  it  nitric  acid  diluted 
with  six  times  its  weight  of  water.  The  acid  is  added 
as  long  as  an  effervescence  takes  place,  and  we  heat 
the  vessel  gently.  If  all  the  substance  be  dissolved, 
we  conclude  that  there  is  no  sulphate  of  lead.  Should 
there  be  an  insoluble  deposit,  we  throw  the  whole 
upon  a  filter  and  wash  it  thoroughly.  The  sulphate 
of  lead  collected  is  then  dried  and  weighed.  Let  us 
suppose  that  its  weight  is  7  grammes.  The  filtered 
liquor  contains  chalk  and  the  dissolved  white  lead ; 
their  separation  is  effected  by  adding  ammonia  until 
the  liquor  smells  of  it  slightly.  The  precipitate 
of  oxide  of  lead  is  collected  upon  a  filter,  washed, 
dried  and  weighed.  Let  the  supposed  weight  be  10 
grammes ;  we  know  that  100  parts  of  oxide  of  lead 
are  equal  to  119.78  parts  of  white  lead ;  therefore  10 
grammes  of  oxide  represent  11.978  grammes  of  white 
lead,  that  is,  12  grammes  without  fractions.  De- 
ducting from  the  25  grammes  of  sample  the  sum  of 
the  weights  of  sulphate  and  carbonate  of  lead,  there 
remain  6  grammes  of  carbonate  of  lime.  Lime  may 
be  ascertained  and  determined  by  pouring  into  the 
liquor,  filtered  from  the  oxide  of  lead,  a  solution  of 
oxalate  of  ammonia  which  will  produce  a  white  pre- 
cipitate of  oxalate  of  lime.  The  results  are  only 
approximate,  as  we  do  not  wish  to  complicate  the 
operations  which  require  a  certain  amount  of  chemical 
knowledge  in  order  to  operate  with  certainty.  We 
have  also  found  samples  of  white  lead  which  were 
mixed  with  sulphate  of  baryta  or  clay;  these  sub- 
stances remain  in  the  insoluble  residuum. 

Here  are  the  processes  employed  by  Mr.  Louyet 
for  ascertaining  the  impurities  of  white  lead : — 
9 


130 


MANUFACTURE  OF  COLORS. 


"I  was  intrusted,  some  time  since,  with  three 
different  samples  of  white  lead,  intended  for  exporta- 
tion. It  is  probable  that  the  destination  of  these  pro- 
duets  induced  the  manufacturer  to  think  that  it  was 
useless  to  remain  within  bounds,  and  that  the  ignorance 
of  the  consumers  would  prevent  them  from  ascertain- 
ing that  what  was  sold  as  white  lead  could  be  as  pro- 
perly called  sulphate  of  baryta  as  white  lead. 

"One  gramme  of  sample  No.  1,  heated  to  redness 
in  a  platinum  crucible  until  complete  trans- 
formation into  oxide  of  lead,  gave  a  loss  of    .    0.100  gramme. 

"A  second  calculation  gave  the  same  weight. 

"  For  one  gramme  of  sample  No.  2,  calcined  in 

the  same  manner,  the  loss  was  .  .  .  0.049  gramme. 
"  Sample  No.  3,  1  gramme,  loss    ....    0.037  " 

"The  calcined  product  No.  1  was  boiled  with  pure 
nitric  acid,  then  water  was  added  and  the  boiling  con- 
tinued. The  insoluble  residuum  was  yellowish,  al- 
though the  liquor  was  strongly  acid.  After  filtration 
the  residue  was  well  washed  with  boiling  water  and 
calcined.  Its  weight  was  0.805  gramme  after  de- 
ducting the  ashes  of  the  filter. 

"I  will  observe  that  the  residuum  of  'No.  1  was 
darker  than  that  of  No.  2,  and  this  latter  darker  than 
No.  3,  which  was  quite  white.  The  residuum  of  No. 
1,  after  being  heated  with  the  blowpipe  upon  charcoal 
and  with  soda,  stained  a  permanent  black  the  piece  of 
silver  upon  which  it  had  been  put  wet. 

"This  is  a  characteristic  of  sulphates.  It  was 
proved  that  the  sulphate  mixed  with  the  carbonate 
of  lead  was  sulphate  of  baryta,  by  boiling  it  with  a 
solution  of  carbonate  of  soda,  filtering,  and  dissolving 
the  washed  residue  upon  the  filter  with  hydrochloric 


WHITE  COLORS.  131 

acid.  The  liquor  obtained  gave  a  heavy  white  pre- 
cipitate with  sulphuric  acid. 

"The  solution  resulting  fi'om  the  treatment  of 
white  lead  ^^o.  1  with  nitric  acid  was  precipitated 
with  sulphuric  acid,  and  the  calcined  sulphate  of 
lead  weighed  0.765  gramme,  corresponding  to  0.563 
gramme  of  oxide  of  lead,  or  0.674  gramme  of  neutral 
carbonate.  Calculated  from  the  proportion  of  oxide 
of  lead,  that  of  carbonic  acid  is  0.111  gramme,  whereas 
the  loss  by  calcination  of  the  white  lead  is  only  0.100 
gramme.  I  admit  that  this  difference  is  due  to  the 
fact  that  all  of  the  oxide  of  lead  is  not  carbonated, 
but  that  a  certain  proportion  remains  in  the  hydrated 
state.  But,  as  the  equivalent  of  water  is  smaller 
than  that  of  carbonic  acid,  it  follows  that  the  number 
is  too  high  if  we  suppose  that  all  of  the  oxide  is  com- 
bined with  carbonic  acid,  and  we  must  subtract  0.011 
from  0.674;  there  remains  0.663  gramme.  White 
lead  'No.  2  was  treated  in  the  same  manner,  and 
the  residue  msoluble  in  nitric  acid  weighed  0.660 
gramme  after  being  washed  and  calcined.  The  pro- 
portion of  sulphate  of  lead  from  the  nitric  solution 
was  0.360  gramme,  corresponding  to  0.264  gramme 
of  protoxide  of  lead.  But  here  the  number  calcu- 
lated for  carbonic  acid  differs  but  little  from  that 
found  by  direct  expei-iment.  In  this  case,  as  in  the 
former,  the  number  obtained  for  carbonate  of  lead  is 
a  little  low,  and  the  loss  may  be  added  to  it.  Indeed, 
the  sulphate  of  lead  is  slightly  soluble  in  acid  liquors, 
and  the  precipitation  by  the  oxalate  of  ammonia 
would  have  given  more  accurate  results.  It  follows 
that  the  calculated  number  for  carbonic  acid  would 
have  been  a  little  higher,  and  above  that  found  by 
direct  experiment. 


182 


MANUFACTURE  OF  COLORS. 


"  But  I  repeat  the  observation  already  made,  that  a 
portion  of  the  oxide  of  lead  in  white  lead  is  in  the 
hydrated  state.  One  gramme  of  the  sample  No.  3 
gave  an  insoluble  residuum  equal  to  0.718  gramme, 
and  a  precipitate  of  sulphate  of  lead  weighing  0.277 
gramme,  which  corresponds  to  0.203  of  oxide  of  lead 
or  0.243  of  carbonate  of  lead. 

"  The  composition  of  the  samples  was,  therefore,  as 
follows : — 

White  lead.     Sulphate  of  baryta. 

1  gramme  sample  No.  1  .  .  .  0.695  0.305 
1       "  "     No.  2  .       .       .    0.340  0.660 

1       "  "     No.  3  .       .       .    0.282  O.nS 

"  These  analyses,  the  last  one  especially,  show  that 
I  was  right  in  saying  that  these  products  may  in- 
differently be  called  white  lead  or  sulphate  of  baryta." 

"White  lead  is  often  mixed  with  that  sulphate  of 
baryta  which  is  called  hlancfixe  or  haryta  ivMte,  and 
which  is  prepared  from  the  carbonate  of  baryta.  It 
is  an  adulteration  which  ceases  to  be  objectionable 
when  the  manufacturer  makes  the  composition  known. 

Belgian  and  German  manufacturers  sell  various 
qualities  of  white  lead,  the  compositions  of  which  are 
known  by  the  names  they  bear ;  thus  : — 

1.  Krems  white  is  a  pure  white  lead ; 

2.  Venice  white  is  a  mixture  of  equal  parts  of  sul- 
phate of  baryta  and  white  lead  ; 

3.  Hamburg  white  is  a  mixture  of — 

Sulphate  of  baryta  2  parts. 

White  lead        .       .       .       .       .       .1  part. 

4.  Holland  white  is  composed  of — 

Sulphate  of  baryta  3  parts. 

White  lead  1  part. 


WHITE  COLORS. 


133 


-  A  bluish  tinge  is  often  imparted  to  white  lead 
with  a  small  proportion  of  indigo. 

It  is  said  that  the  following  mixtures  are  generally 
found  in  the  French  color  trade : — 

White  lead.     Sulphate  of  baryta. 

White  lead  (superfine) .       .       .    85  15 

No.  1         .       .       .    YO  30 

No.  2        ...    60  40 

No.  3        .       .       .40  to  50  60  to  50 

In  order  to  ascertain  whether  a  sample  of  white 
lead  is  mixed  with  sulphate  of  baryta  or  sulphate  of 
lead,  it  is  treated  with  nitric  acid  diluted  with  two  or 
three  parts  of  distilled  water.  Pure  white  lead  is 
entirely  dissolved,  whereas  the  above  sulphates  remain 
unacted  upon  by  the  reagent. 

Mr.  A.  Bacco  has  indicated  a  simple  process  by 
which  white  leads  may  be  tested  by  the  wet  way. 

"  The  quality  of  white  leads,"  says  he,  "  as  every 
chemist  knows,  depends  on  their  extreme  opacity, 
which  is  the  greater  as  their  molecules  are  amorphous 
and  their  composition  more  basic.  In  experimenting 
upon  a  crystalline  white  lead,  with  little  body,  I  have 
ascertained  that  it  may  be  improved  by  digesting  it 
in  a  carbonated  alkaline  solution,  rendered  slightly 
caustic  by  an  addition  of  a  small  quantity  of  quick- 
lime.   The  entire  operation  is  performed  in  the  cold. 

"But  as  a  white  lead  should  be  basic,  in  order  to 
have  body,  I  have  tried  a  process  for  ascertaining 
whether  a  white  lead  is  more  or  less  basic,  and  I 
have  succeeded  with  a  solution  of  neutral  chromate  of 
potassa  poured  upon  wet  white  lead.  This  latter 
substance  is  converted  into  a  chromate  of  lead,  which 
is  neutral,  basic,  or  six  basic,  according  as  the  white 


134 


MAN^UFACTURE  OF  COLOKS. 


lead  itself  is  more  or  less  basic,  and  the  degree  is 
shown  by  a  change  of  coloration. 

"If  the  chromate  be  lemon-yellow,  the  white  lead 
is  neutral  and  of  inferior  quality ;  an  orange  color 
indicates  a  white  lead  slightly  basic,  but  if  the  color 
be  a  scarlet-red  we  ma}^  be  sure  that  the  white  lead 
is  highly  basic.  Indeed,  every  chemist  knows  that 
the  neutral  chromate  of  lead  is  lemon-yellow,  the  tri- 
basic  orange-yellow,  and  the  six-basic  fire-red. 

"We  may  then  conclude  that  the  degree  of  colora- 
tion thus  obtained  gives  a  sure  indication  of  the 
quality  of  white  leads." 

All  these  methods  of  ascertaining  the  purity  of 
white  leads  appear  to  us  far  from  entirely  satisfactory ; 
and,  by  reading  the  following  paragraph,  it  will  be 
seen  that  the  composition  of  this  product  is  not  so 
simple  as  is  supposed,  and  that  a  thorough  chemical 
analysis  will  alone  give  correct  indications  of  the 
quality  of  white  lead. 

1.7th.  Gompoiiition  of  White  Leads, 

Mr.  Mulder,  of  Utrecht,  has  published  the  results 
of  experiments  made  by  Mr.  Vlaandern  upon  the 
composition  of  twenty-seven  samples  of  white  lead  of 
Holland  manufacture.  The  results  are  sufficiently 
interesting  to  be  reproduced  here.  In  the  analyses 
the  hygroscopic  water  has  not  been  determined  sepa- 
rately. 

I.  II.      Calculated.  Equivalents. 

CO^  .       .       .       .    11.4       11.4  11.4    =  2 

HO  .       .       .       .     2.3         2.4  2.3    =  1 

PbO  .       .       .       .    86.4       86.5  86.3    =  3 

or 

PbO,HO  -I-  2CO^PbO. 


WHITE  COLORS. 


135 


CO"- 
HO 
PbO 


III.  IV. 

12.4  12.2 

2.0  2.1 

85.0'  85.6 


V. 

12.0 
2.0 
85.9 


VI. 

12.4 
2.1 
85.7 


VII. 

12.0 
2.0 
86.1 


VIII. 

12.3 
2.1 
85.4 


IX. 

12.3 
2.3 

85.5 


X. 

12.0 
1.8 

85.6 


XI. 

12.3 
2.1 
85.5 


or 


2rbO,HO  -f  5CO^PbO. 


XIII. 

XIV. 

XV. 

XVI. 

co^ 

12.7 

12.7 

12.5 

12.7 

HO 

2.3 

1.7 

2.1 

1.9 

PbO 

85.2 

85.5 

85.8 

85.4 

XVII. 

12.5 
1.9 
85.7 


XVIII. 

12.9 
1.2 

85.3 


XIX. 

12.9 
2.1 
85.1 


Calcu-  Equiva- 
XII.   lated.  lentB. 
12.2    12.2  =  5 
2.0     2  0  =  2 
85.6    85.8  =  7 


Calcu-  Equiva- 
lated.  lents. 
12.7  =  3 
1.7  =  1 
85.6  =  4 


or 


PbO,HO+3CO%PbO. 


co^ 

HO 
PbO 


XX. 

13  1 

2.0 
83.4 


XXI. 

13.5 
1.5 
84.7 


XXII. 

13.5 
1.6 

84  9 


XXIII.  XXIV. 

13.2  13.0 

1.7  1.8 

85.2  85.2 


XXV. 

13.3 
1.8 
85.1 


XXVI. 

13.2 
1.9 
85.0 


XXVII. 

13.1 
2.0 
85.1 


Calcu-  Equiva- 
lated.  lents. 
13.4  =  4 
1.4  =  1 
85.2  =  5 


or 


PbO,HO  +  4CO',PbO. 

Thus,  the  samples  of  white  lead  which  were  ex- 
amined had  the  following  compositions  : — 

Two,  PbO,HO  +  2CO^PbO. 
Ten,  2PbO,HO  +  5CO^PbO. 
Seven,  PbO,HO  +  SCO^PbO. 
Eight,   PbO,HO +  4CO%PbO. 

Therefore,  Holland  white  lead  is  a  hydrated  oxide 
of  lead  with  2,  2|,  3,  or  4  equivalents  of  neutral 
carbonate  of  lead.  2  and  3  are  met  with  in  the  trade 
not  so  frequently  as  2|  and  4. 

Mr.  Mulder  regrets  that  he  does  not  know  the 
manufacturers  by  whom  these  products  were  made, 
because  he  would  then  have  been  able  to  ascertain 
whether  the  white  lead  of  a  given  manufacture  pre- 
served the  same  composition. 

On  the  other  hand,  Mr.  W.  Baker  has  demonstrated 
that  white  lead  made  by  the  Holland  process  has  no 
fixed  composition,  but  that  it  is  a  carbonate  of  lead 
holding  a  variable  proportion  of  hydrated  oxide. 


136 


MANUFACTURE  OF  COLORS. 


which  depends  on  the  conditions  attending  the  cor- 
roding process.  Thus,  from  the  same  bed,  using  the 
same  tan  and  acetic  acid,  samples  may  be  taken  pre- 
senting variable  proportions  of  carbonate  and  hydrate 
of  lead.  Near  the  walls,  where  the  aqueous  and  car- 
bonic vapors  escape  freely,  there  are  sometimes  found, 
under  certain  circumstances,  small  translucent  crys- 
tals of  neutral  carbonate  with  a  sweet  taste.  On  the 
corroding  surface  there  is  often  seen  a  thin  crust,  the 
composition  of  which  is  nearly  that  of  the  neutral 
carbonate.  The  quantity  and  the  quality  of  the 
water  employed  in  grinding  and  washing  white  lead 
have  also  an  effect  on  the  composition  of  the  product. 
Here  are  a  few  analyses  of  dry  white  lead  from  various 
manufacturers,  which  quite  agree  with  those  of  Mr. 
Mulder. 


No.  I. 

Calculated. 

Equivalents. 

CO^  . 

.  11.03 

11.4 

=  2 

HO  . 

.  2.23 

2.3 

=  1 

PbO  . 

.  86.11 

86.3 

=  o 

No.  II. 

CO^  . 

.  12.17 

12.7 

=  3 

HO 

.  1.66 

1.7 

=  1 

PbO  . 

.  85.37 

85.6 

=  4 

No.  III. 

No.  IV. 

CO'' 

.  13.37 

13.48 

13.4 

=  4 

HO 

.  1.11 

1.46 

1.4 

=  1 

PbO  . 

.  84.71 

84.88 

85.2 

=  5 

The  hygroscopic  water  does  not  generally  amount 
to  more  than  0.05  per  cent. 

The  white  lead  ]S^o.  I.  was  from  London,  No.  II. 
from  Newcastle,  and  Nos.  III.  and  IV.  from  Sheffield. 

Moreover,  what  still  demonstrate  the  variety  in  the 
composition  of  white  leads  are  the  following  analyses 
of  crusts  separated  from  the  leads : — 


WHITE  COLORS. 


137 


CO^. 

HO. 

PbO. 

No.  1.  Solid  crust  of  good  quality 

12.49 

1.60 

85.24 

No.  2.    "        "          u       t4             ^  ^ 

12.31 

1.73 

85.77 

No.  3.  Crust  with  scaly  surface 

15.14 

0.53 

83.86 

No.  4.  Hard  crust,  not  very  deeply  corroded 

15.14 

0.60 

84.10 

No.  5.  Colorless,  crystalline,  and  tranlucent 

crusts  

15.71 

0.75 

83.53 

No.  6.  Colorless  and  crystalline  crusts  taken 

from  a  mass  sweet  to  the  taste  . 

16.11 

0.49 

83.39 

No.  *7.  Neutral  carbonate,  calculated 

16.50 

83.50 

It  is  evident  that  Nos.  5  and  6  are  neutral  car- 
bonate with  a  trace  of  hydrate,  and  that  I^os.  3  and  4 
show  the  passage  from  the  neutral  carbonate  to  the 
normal  corroded  product,  the  composition  of  which 
may  be  represented  by  the  formula — 
PbO,HO  +  3CO^PbO. 

18th.  Processes  for  Rendering  the  Manufacture  of  White  Lead 
less  Unhealthy. 

The  manufacture  of  white  lead  presents  various 
manipulations  which  are  quite  unhealthy,  because  of 
the  continual  handling  of  a  poisoning  substance,  and 
especially  of  the  white  lead  dust  flying  about  the 
work-rooms  and  being  inhaled  by  the  men. 

The  cause  of  humanity  before  all,  and  possibly  an 
economy  in  the  manufacture,  demand  of  us  to  search 
for  the  means  of  diminishing  the  danger.  It  is  only 
of  late  that  this  question  in  public  hygiene  has  been 
brought  into  serious  consideration,  and  has  been  suc- 
cessfully resolved.  We  owe  much  in  this  respect  to 
the  exertions  of  the  "  Societe  d'Encouragement,"  and 
we  shall  borrow  from  its  bulletin  a  few  interesting 
documents  which  relate  to  successful  improvements 
carried  into  this  manufacture. 


138 


MANUFACTURE  OF  COLORS. 


A.  The  Ward  Machine  for  the  3fanafacture  of  White  Lead. 

In  order  to  appreciate,  at  its  real  value,  the  inven- 
tion of  this  machine,  we  should  remember  that  white 
lead  is  a  powerful  poison,  which,  by  the  ordinary  pro- 
cesses, is  reduced  into  a  very  fine  dust,  penetrating 
the  pores  of  the  skin,  the  respiratory  organs,  and  the 
lungs.  Thus,  the  clothes  of  the  men  working  in 
such  a  manufacture  are  constantly  impregnated  with 
this  impalpable  powder,  in  the  same  manner  as  those 
of  millers  are  with  flour. 

The  health  of  these  poor  men  is  soon  seriously  im- 
paired, their  complexions  become  livid,  and  they  soon 
fall  into  a  state  of  languor  and  consumption,  pro- 
duced by  inflammation  of  the  viscera.*  In  a  few 
years  they  decay  and  die  before  the  time  nature  had 
allotted  to  them. 

It  is,  therefore,  a  great  humanitarian  service  to 
endeavor  to  preserve  from  death  so  many  men  working 
in  this  dangerous  manufacture,  and  Mr.  Ward  thinks 
that  he  has  attained  this  great  result,  which,  however, 
has  also  attracted  the  attention  of  Messrs.  Schuzen- 
bach  and  Gannel. 

His  apparatus  comprises: — 

I.  A  trough,  4  metres  long,  2  metres  wide,  and 
1.30  metres  deep. 

II.  Two  brass  rollers,  superposed,  for  grinding  the 
substances.  The  lower  one  is  entirely  immersed  in 
water,  and  the  upper  one  partly  so,  their  line  of  con- 
tact being  30  centimetres  below  the  level  of  the 
water.    Motion  is  imparted  to  them  by  means  of  a 

*  In  the  autopsy  of  men  from  white  lead  works,  lead  was  always 
found  attached  to  the  viscera.  There  was,  therefore,  no  doubt  of 
their  premature  death  and  of  the  cause  of  it. 


WHITE  COLORS. 


139 


crank  or  pulley,  fixed  to  the  axis  of  the  upper  cylin- 
der, which  is  connected  with  the  lower  one  by 
pinions. 

Counterweights  are  also  fixed  to  the  extremities  of 
the  upper  axis,  giving  a  sufiicient  pressure,  and,  at 
the  same  time,  allowing  an  upward  motion  of  the 
cylinder,  should  too  great  a  mass  of  metal  become 
engaged  between  the  rolls. 

III.  An  oaken  platform,  perforated  with  a  quantity 
of  holes,  15  or  16  millimetres  in  diameter,  and  serving 
as  a  sieve  for  the  material  which  leaves  the  rolls. 
This  platform  is  maintained  at  about  8  centimetres 
below  the  rollers  by  means  of  wooden  blocks  (hold- 
fasts) above  and  below  it. 

IV.  A  wooden  inclined  plane  for  feeding  the 
rollers. 

An  outlet  is  left  on  one  side  of  the  trough  for  the 
water.  The  white  lead,  which  is  quite  finely  pul- 
verized, falls  easily  through  the  holes  of  the  platform, 
whereas  the  laminated  metal  remains  on  top  and  is 
raked  out. 

As  the  non-corroded  metal  is  separated  from  the 
white  lead  entirely  under  water,  no  dangerous  dust  can 
be  raised. 

Lastly,  the  metallic  plates  are  allowed  to  drain 
upon  an  inclined  trough,  and  to  become  dry  before 
they  are  used  or  melted  anew. 

"It  may  be  inquired,"  says  the  inventor,  "why 
the  substances  are  not  wetted  before  passing  through 
the  rolls.    The  answer  is  this  : — 

"1.  They  would  become  pasty,  and  their  passage 
through  the  rolls  be  difficult. 

"2.  This  paste  would  not  be  well  sifted. 

"3.  A  certain  proportion  of  metallic  lead  is  neces- 


140 


MANUFACTURE  OF  COLORS. 


sary  to  the  operation,  and  should  not  be  removed 
before  the  substances  are  passed  through  the  cylin- 
ders." 

Fig.  25  shows  the  apparatus,  which  has  been 
already  explained. 


Fig.  25. 


A,  inclined  plane  for  feeding  the  i-ollers. 

B,  the  superposed  brass  rollers  for  grinding  the 
substances. 

c,  wooden  trough. 

D,  oaken  partition  perforated  with  holes. 

E,  crank,  here  indicated  as  a  means  of  imparting 
motion.  It  can  be  substituted  by  pulleys,  for  in- 
stance, driven  by  water  or  steam  power. 

F,  pinion  fixed  to  the  axis  of  the  upper  cylinder, 
and  driving  the  lower  one. 

G  G,  two  counterweights  bearing  upon  the  axis  of 
the  upper  roller. 
H,  water  outlet. 

B.  Apparatus  of  Mr.  Th.  Lefevre  for  Pulverizing  White  Lead. 

Mr.  Th.  Lefevre,  manufacturer  of  white  lead  at 
Lille,  patented,  in  1849,  an  apparatus  for  grinding 
white  lead,  the  description  of  which  is  as  follows : — 


WHITE  COLORS. 


141 


"  The  ordinary  process  for  pulverizing  white  lead 
blocks  consists  in  grinding  them  between  two  hori- 
zontal stones,  the  upper  one  of  which  is  revolving. 
The  powder  is  then  sifted  in  order  to  separate  the 
coarse  portions.  This  mode  of  operation,  whatever 
be  the  precautions  taken,  is  open  to  the  objection  of 
producing  in  the  works  a  very  light  dust  of  white 
lead,  which  is  inhaled  by  the  men  and  produces  that 
dangerous  sickness  called  lead  colic. 

"  We  have  tried  to  replace  this  dangerous  method 
by  one  presenting  no  cause  of  insecurity  to  the  men, 
and  we  have  succeeded  by  the  use  of  an  apparatus 
actually  in  operation  in  our  own  works. 

"  Instead  of  working  two  horizontal  stones  in  the 
open  air,  we  keep  them  in  a  tight  inclosure.  The 
lower  stone  is  steady,  whereas  the  upper  one  re- 
volves and  receives  its  motion  from  a  vertical  shaft 
passing  through  the  middle  of  the  lower  stone,  and 
fixed  to  a  three-branched  rynd  in  the  upper  one.  A 
copper  cover  screwed  upon  the  casing  of  the  stones, 
supports  the  distributor  of  white  lead.  This  distri- 
butor is  made  of  two  truncated  cones,  one  of  which, 
the  exterior,  is  bolted  upon  the  copper  cover.  The 
interior  one  is  fixed  to  a  vertical  revolving  shaft. 
Both  cones  are  cast  with  grooves  in  opposite  direc- 
tions. 

"  The  lumps  of  white  lead  are  first  reduced  in  size 
in  the  distributor,  then  finely  powdered  between  the 
stones,  and  lastly,  sifted  in  sieves  kept  in  hermetically 
closed  boxes. 

"Fig.  26  is  a  vertical  section  of  the  apparatus 
passing  through  the  line  a  b  c  d  (Fig.  27). 

"Fig.  27  is  a  horizontal  section  passing  through 
the  line  e  f  g  h  (Fig.  26). 


WHITE  COLORS. 


143 
Fig.  28. 


Fi2.  30. 


"  Fig.  30  is  the  distributor  on  a  larger  scale. 
"  This  distributor  is  made  of  cast-iron  and  is  lined 
inside  with  a  bronze  casting  filled  with  grooves. 
Another  grooved  cone  A  revolves  inside,  and 
breaks  the  lumps  or  blocks  of  white  lead 
into  small  fragments,  which  fall  between 
the  stones  G  k. 

"  B,  vertical  iron  shaft,  fixed  to  the  small 
distributing  cone,  and  rising  up  to  the 
capital  c,  on  top  of  which  there  is  a  screw 


144 


MANLTFACTLTRE  OF  COLORS. 


which  allows  of  the  raising  or  lowering  of  the  shaft, 
in  order  to  regulate  the  delivery  of  the  white  lead  to 
the  stones  a  k. 

"c,  cast-iron  capital  supported  by  four  columns, 
and  which  maintains  the  vertical  shaft  in  its  bearing-s. 

"d,  f  conical  gearing  driving  the  shaft  b  by  means 
of  the  pulley  E,  fixed  upon  the  horizontal  shaft  f'. 

G,  upper  stone  of  white  marble,  which  could  be 
substituted  by  a  burr-stone.  A  three-branched  rynd  is 
fixed  in  the  central  opening,  and  receives  the  shaft  i. 
The  under  surface  of  the  stone  (Figs.  31  and  32)  has 


Fig.  31.  Fig.  32. 


three  grooves  or  ways  J  J  J  for  delivering  the  pulver- 
ized white  lead. 

"  K,  lower  steady  stone  of  the  same  material  as  the 
upper  one  and  grooved.  It  is  perforated  in  the  centre 
with  a  square  hole  which  is  filled  with  a  box  l  of 
iron  on  the  sides,  and  copper  on  the  top. 

"  This  box  is  divided  into  six  compartments,  three 
for  the  grease  and  three  for  the  brasses.  The  latter 
are  regulated  by  the  screws  n  n  K.  Three  or  four 
screws  p  p  maintain  the  level  of  the  stone. 

"The  stones  are  supported  by  a  framework  upon 
which  is  screwed  a  hermetical  copper  cover,  bearing 
the  distributor  of  the  white  lead. 

"  Between  the  stones  and  their  casing  there  is  an 
empty  space  p',  which  receives  the  projected  white 
lead.     Two  opposite  openings  deliver  it  into  the 


WHITE  COLORS. 


145 


rectangular  zinc  spouts  o  o,  which,  in  their  turn,  con- 
duct the  pulverized  material  into  the  revolving  sieves 
o'  o',  held  in  hermetically  closed  boxes.  These  sieves 
are  a  check  on  the  neglect  of  the  men,  because  the 
stones,  when  properly  set,  grind  well  enough  without 
the  necessity  of  sifting. 

"  Q  R,  conical  gearing  driven  by  the  fixed  pulley 
T.    t'  is  a  loose  pulley. 

"  u  u,  brackets  supporting  the  shaft  s. 

"  V  conical  gear  driving  a  pulley  y  fixed  upon 
the  shaft  x,  and  transmitting  its  motion  to  the  pulley 
E  of  the  distributor. 

"  z,  pulley  on  the  shaft  s  driving  the  two  sieves 
o'  o'  by  means  of  the  pulley  and  pinions  b' d'  e'. 

"  The  shaft  of  the  revolving  stone  stands  upon  a 
cast-iron  or  steel  step  a'  fixed  upon  cross-bars  h'  bolted 
to  the  four  columns  i'. 

"  j',  screw  under  a'  for  raising  or  lowering  the 
upper  stone  G, 

main  driving  shaft  upon  which  are  fixed  the 
pulleys  l'." 

Mr.  Th.  Lefevre  has  not  only  invented  the  above 
described  apparatus,  but  he  has  since  organized  his 
works  on  an  entirely  salubrious  system  of  manu- 
facture. We  cannot  describe  it  better  than  by  present- 
ing the  report  made  by  MM.  Barreswill,  Salvetat,  and 
Chevalier  to  the  "  Societe  d'Encouragement." 

The  works  of  Mr.  Th.  Lefevre,  founded  in  1825,  have 
since  then  received  many  improvements.  A  steam- 
engine  of  thirty  horse-power  gives  motion  to  all  the 
machinery  of  the  works.  Several  small  railroads 
carry  the  crude  or  prepared  materials  in  every  direc- 
tion, and  are  a  great  saving  of  arduous  labor. 

Gas  is  manufactured  in  the  place,  and  is  used  from 
10 


146 


MANUFACTUIiE  OF  COLORS. 


120  burners.  The  stack  of  the  gas  furnace  is  33 
metres  high.  The  retorts  are  made  of  clay,  and  the 
cracks  are  closed  with  a  mixture  of  powdered  glass, 
borax,  and  pipe  clay. 

There  are  from  eighty  to  one  hundred  and  twenty 
men  employed  in  the  works,  the  smaller  number 
in  dull  times.  Mr.  Lefevre  produces  yearly  from 
1,600,000  to  1,800,000  kilogrammes  of  white  lead 
thus  subdivided : — 

White  lead  in  scales  from  .  .    45  to  50,000  kilogrammes 

"             "  lumps  .  .  300  "  350,000  " 

"           powdered    "  .  1100     1,200,000  " 

"       ground  in  oil    "  .  .  150  "  200,000  " 

The  consumption  of  the  latter  article  increases 
daily  and  its  manufacture  follows  the  progression. 

The  good  quality  of  the  products  of  these  works 
has  been  acknowledged  in  the  national  exhibitions, 
and  at  the  World's  Fair,  London. 

The  mode  of  manufacture  is  the  Holland  process, 
and  we  shall  successively  describe  the  operations 
which  we  have  seen  practised. 

Casting  of  the  lead. — This  operation  is  effected  in  a 
special  room  called  the  foundry,  and  the  lead  employed 
is  either  new  metal  or  that  which  has  not  been  entirely 
corroded.  In  the  latter  case  certain  precautions  are 
taken  to  protect  the  men  from  the  vapors  produced 
during  the  fusion.  Thus  the  metal  is  put  through 
front  sliding-doors,  into  a  cast-iron  kettle  entirely 
covered  with  a  hood,  the  top  of  which  communicates 
by  means  of  a  pipe,  with  the  stack  of  the  furnace,  12 
metres  high,  and  having  a  strong  draft. 

Before  being  put  into  the  kettle,  the  lead  is  for 
some  time  kept  in  a  hot  place,  where  all  dampness  is 
removed.    Thus  is  avoided  the  danger  of  the  molten 


WHITE  COLORS. 


147 


metal  being  thrown  ont,  as  when  wet  lead  is  introduced 
into  a  fused  bath. 

When  the  lead  is  melted,  it  is  cast  into  sheets 
about  60  centimetres  long,  10  wide,  and  a  few  milli- 
metres thick,  and  weighing  1  kilogramme  on  an 
average.  These  sheets  are  then  carried  into  another 
and  adjoining  room,  where  they  are  cut  in  two  and 
rolled  into  the  shape  of  a  spiral  which  fills  the  pots  of 
the  beds. 

These  operations  present  none  or  very  little  danger. 
In  nineteen  years,  a  single  melter  only  has  suffered 
from  lead  disease. 

Building  the  beds, — There  are  forty-eight  beds  at 
the  works  of  Mr.  T.  Leftvre  at  Moulins-Lille.  They 
are  stone  built,  and  begin  at  1  metre  below  the  level 
of  the  ground.  Their  dimensions  are  5  metres  long, 
4  wide,  and  6  high. 

Stable  manure  is  employed,  but  other  works  use 
spent  tan.  In  the  latter  case  the  operation  is  slower, 
and  requires  from  sixty  to  ninety  days,  instead  of 
forty,  as  with  stable  manure. 

A  banquette,  30  centimetres  wide  and  40  high,  is 
built  around  the  bed  with  the  manure  from  a  preceding 
operation,  while  the  middle  is  filled  with  a  layer  of 
fresh  manure  40  centimetres  high.  This  first  layer 
receives  about  1200  pots,  into  each  of  which  there  is 
poured  about  a  fourth  of  a  litre  of  vinegar.  A  spiral 
of  lead  is  then  put  into  each  pot,  and  rests  upon  two 
inside  knobs  which  prevent  it  from  touching  the 
vinegar. 

The  whole  is  then  covered  with  flat  leaden  sheets, 
then  with  pieces  of  scantling  from  10  to  12  centime- 
tres square,  in  order  to  leave  room  for  a  draft,  and 
lastly  with  boards.   Another  banquette  of  old  manure 


148 


MAT^UFACTURE  OF  COLOKS. 


is  formed  upon  the  first  layer,  and  the  middle  space  is 
filled  with  fresh  manure.  Pots,  vinegar,  and  lead  are 
arranged  as  previously  explained,  and  the  building  up 
of  the  bed  goes  on  until  there  are  seven  or  eight 
layers. 

In  about  six  weeks  the  conversion  of  the  lead  into 
carbonate  is  complete,  or  nearly  so. 
On  an  average,  each  bed  requires — 

1.  8  two-horse  loads  of  stable  manure ; 

2.  300  litres  of  vinegar  per  layer,  or  2400  per  bed; 

3.  1200  to  1500  kilogrammes  of  lead  per  layer,  oi* 
from  10,000  to  12,000  kilogrammes  per  bed. 

Four  men  build  two  layers  per  day,  or  a  bed  in 
four  days :  that  is,  sixteen  days  work  per  bed. 

There  is  no  insalubrity  in  the  building  of  the  beds. 
Gas-burners  may  be  used  when  desired. 

TaMng  the  beds  aj)art — When  the  time  necessary 
for  the  corrosion  of  the  lead  has  expired,  the  beds  are 
taken  apart  in  the  following  manner:  The  manure, 
boards,  and  pieces  of  scantling  of  the  top  layer  are 
removed.  The  corroded  lead  is  then  emptied  into  a 
small  wooden  box,  and  the  largest  portions  of  uncor- 
roded  metal  are  picked  apart.  There  must  be  a  little 
dust  produced,  but  the  testimony  of  many  workmen 
is  that  this  operation  is  attended  with  very  little 
danger  to  health.  In  another  establishment  at  Lille, 
the  men  are  allowed  to  smoke  when  taking  the  beds 
apart,  and  the  manager  certifies  that  many  cases  of 
sickness  are  thus  prevented. 

In  Mr.  Woelmann's  works  the  lead  from  the  beds  is 
never  melted  anew ;  the  un corroded  portions  are  used 
for  covering  the  pots. 

12.000  kilogrammes  of  lead  give  on  an  average: 
First,  carbonated  lead  10,000  kilogrammes;  second, 


WHITE  COLORS. 


149 


non-corroded  lead  4000  kilogrammes.  Therefore,  the 
increase  of  weight  of  the  8000  kilogrammes  of  lead 
which  are  corroded  is  25  per  cent. 

The  taking  apart  of  the  beds  is  done  with  naked 
hands.  Gloves  are  not  very  handy  to  work  with 
unless  they  are  very  supple,  in  which  case  they  be- 
come expensive. 

Picking  up, — Before  1842  the  white  lead  from  the 
beds  was  carried  to  the  picking  room,  where  the  car- 
bonate was  separated  from  the  metal.  As  this  opera- 
tion requires  the  beating  and  unrolling  of  the  sheets, 
it  is  very  unhealthy  on  account  of  the  great  quantity 
of  flying  dust.  Strong  drafts  kept  in  the  room  were 
insufficient  as  a  pi»eventive  of  danger,  and  were 
attended  with  loss  of  material.  Moreover  the  opera- 
tion was  slow. 

The  separation  of  the  white  lead  from  the  uncor- 
roded  metal  is  now  effected  in  Mr.  Lefevre's  works  by 
a  special  machine,  kept  separate  in  a  tight  enclosure. 
This  machine  is  on  an  upper  floor,  3  metres  above  the 
ground.  The  metal,  with  the  adhering  white  lead,  is 
carried  by  an  endless  leather  apron  to  a  series  of  two 
pairs  of  grooved  rollers,  which  separate  the  greater 
part  of  the  white  lead.  The  remainder  is  removed 
by  the  friction  of  the  metal  in  a  revolving  drum, 
covered  by  metallic  gauze.  The  white  lead  is  received 
into  a  large  closed  box.  The  portions  of  blue  lead 
which  are  sufficiently  large  are  rolled  up  into  spirals 
for  the  pots,  whereas  the  small  fragments  are  melted 
anew. 

As  soon  as  the  dust  has  subsided,  the  white  lead  is 
removed  from  the  I'eceiving  box. 

Dry  grinding  of  scales  of  white  lead. — Formerly  the 
scales  separated  from  the  metal  were  ground  under 


150 


MANUFACTURE  OF  COLORS. 


vertical  running  stones,  and  the  product  was  sifted, 
what  passed  through  the  sieve  being  mixed  with 
water  and  then  ground  under  horizontal  stones. 

At  the  present  time  the  scales  are  carried  by  me- 
chanical means  to  the  first  story,  and  fall  into  large 
troughs,  from  which  they  are  taken  to  a  hopper 
provided  with  a  distributor.  The  scales  pass  first 
between  two  grooved  rollers,  which  break  them  and 
separate  the  blue  lead  still  remaining.  Three  other 
pairs  of  rollers  bring  the  white  lead  to  the  proper 
degree  of  comminution  for  the  wet  grinding.  All 
this  work,  which  formerly  was  so  dangerous,  is  now 
done  by  machinery,  and  every  precaution  is  taken  to 
prevent  the  escape  of  the  white  lead  dust.  All  of 
the  rollers  are  kept  in  perfectly  tight  casings,  and  the 
whole  apparatus  is  also  enclosed  by  light  partition 
walls.  All  the  doors  are  double.  We  see,  therefore, 
that  in  these  fine  works  all  precautions  that  hygiene 
may  suggest  have  been  taken. 

Orinding  white  lead  in  water, — The  white  lead 
which  has  been  dry  powdered  between  the  rollers,  is 
sifted,  and  the  fine  portions  fall  into  a  closed  cistern 
under  ground,  where  they  are  wet  with  water. 

The  wet  white  lead  is  then  ground  under  horizontal 
stones,  twenty  of  which  are  in  use.  A  soft  paste  is 
thus  obtained,  which  is  received  in  tubs,  and  these 
are  carried  by  mechanical  arrangements  to  the  drying 
room.  There  the  paste  is  put  into  porous  conical 
pots,  which  are  ranged  upon  shelves. 

Drying  rooms, — These  rooms  are  heated  during 
the  winter  by  means  of  large  cast  iron  stoves,  burning 
bituminous  coal.  In  summer  a  proper  ventilation  is 
sufficient  to  dry  the  white  lead. 

Mr.  Lefevre  tried  to  light  the  drying  rooms  with 


WHITE  COLORS. 


151 


the  gas  manufactured  in  the  works,  but  he  has  been 
obliged  to  abandon  the  idea,  since  the  sulphuretted 
hydrogen  of  the  gas  blackened  the  surface  of  the 
lumps  of  white  lead,  transforming  it  into  lead  sul- 
phide. This  inconvenience  we  think  may  be  avoided 
by  carrying  off  the  gases  of  the  combustion  through 
a  hood  and  pipe  placed  above  the  burners  ;  or  by  using 
a  gas  containing  but  a  very  slight  proportion  of  sul- 
phuretted hydrogen. 

The  white  lead  in  pots  remains  for  ten  to  twelve 
days  in  ordinary  drying  rooms,  and  loses  the  greater 
part  of  its  water.  The  lumps  become  consistent,  and 
contract  enough  to  be  easily  removed  from  their  pots. 
Their  desiccation  is  then  completed  upon  the  shelves 
of  other  drying  rooms,  heated  at  from  40°  to  50°  C, 
with  hot  air.  The  lumps  which  have  preserved  their 
shape  are  wrapped  in  blue  paper ;  those  which  have 
been  broken  are  powdered.  The  pots  are  cleaned 
with  iron  knives,  and  as  the  adhering  white  lead  is 
still  moist,  this  operation  is  considered  to  be  quite 
devoid  of  danger. 

Powdering  lump  white  lead. — For  several  years 
the  demand  for  lump  white  lead  has  been  decreasing, 
and  the  greatest  consumption  is  that  of  the  powdered 
product. 

By  the  old  process,  the  lumps  of  white  lead  were 
pulverized  under  vertical  stones  running  upon  hori- 
zontal stone  platforms,  and  the  powder  was  then 
sifted.  Notwithstanding  the  care  and  attention 
which  were  taken,  there  was  always  a  very  fine  dust 
of  white  lead  flying  about  the  rooms,  and  the  men 
were  subject  to  lead  colic. 

Instead  of  vertical  stones  working  in  the  open  air, 
Mr.  Lefevre  employs  horizontal  stones  enclosed  with- 


152 


MAl^^^UFACTURE  OF  COLORS. 


in  a  perfectly  tight  metallic  drum.  The  lower  stone 
does  not  move,  but  the  upper  one  makes  two  hundred 
and  seventy-six  revolutions  per  minute. 

On  the  top  of  the  metallic  drum  there  is  a  kind  of 
coffee  mill,  which  breaks  the  lumps  of  white  lead  be- 
fore they  pass  between  the  stones.  With  four  pairs 
of  such  stones  (white  marble),  it  is  possible  to  powder 
every  day,  31,000  kilogrammes  of  white  lead. 

The  pulverized  product  is  thrown  off  against  the 
drum  by  centrifugal  force,  and  falls  into  closed 
troughs  by  two  diametrically  opposite  openings.  The 
troughs  deliver  it  into  metallic  revolving  sieves, 
enclosed  within  a  box  with  double  doors.  The  sifted 
powder  is  received  in  a  wagon  holding  about  1200 
kilogrammes  of  substance,  which  is  removed  only 
when  the  dust  has  entirely  subsided. 

Since  Mr.  Besancon,  in  his  works  at  Ivry  near  the 
gate  of  Fontainebleau  (Paris),  has  established  appara- 
tus for  grinding  white  lead  in  oil ;  the  employment  of 
this  product  has  increased  so  rapidly,  that  this  manu- 
facturer sells  seven-eighths  of  his  white  lead  ground 
in  oil. 

Mr.  Lefevre  has  also  established  this  preparation  in 
his  works.  The  powdered  white  lead  is  put  with  oil 
into  an  apparatus  similar  to  a  kneading  machine,  the 
blades  of  which  thoroughly  mix  the  substances.  The 
paste  obtained  is  then  passed  through  three  pairs  of 
rollers,  which  laminate  and  finish  it  for  the  packing 
barrels. 

Mr.  Lefevre  also  uses  horizontal  stones  for  grinding 
white  lead  in  oil ;  five  pairs  of  such  stones  are  em- 
ployed, besides  the  twenty  other  pairs  for  the  grind- 
ing in  water. 


WHITE  COLORS. 


153 


The  men  employed  at  grinding  always  wear  gloves 
of  lamb  skin. 

Packing  white  lead, — This  operation  is  often  a 
cause  of  lead  colic.  To  prevent  the  production  of 
dust,  Mr.  Lefevre  lets  the  white  lead  into  the  barrel 
slowly  and  carefally,  and  then  compresses  it  by  means 
of  a  screw,  which  pushes  down  a  wooden  block  of  a 
diameter  slightly  less  than  that  of  the  barrel.  A  new 
addition  of  white  lead  is  compressed  in  the  same 
manner,  and  the  operation  is  continued  until  the 
barrel  is  thoroughly  filled. 

The  packing  of  the  lump  white  lead  is  effected  as 
follows :  Rows  of  lumps,  already  wrapped  in  paper, 
are  formed  as  close  as  possible ;  and  when  the  barrel 
is  half  filled,  it  is  shaken  after  it  has  been  covered 
with  several  thicknesses  of  cloth.  These  are  removed 
when  the  dust  has  subsided ;  but  there  is  very  little 
dust  when  the  lumps  are  wrapped  in  paper.  The 
packer  has  always  two  barrels  on  hand,  so  as  not  to 
lose  time,  and  when  one  is  filled,  the  cover  is  imme- 
diately put  on. 

All  the  rooms  in  Mr.  Lefevre's  works  are  kept  per- 
fectly clean,  and  the  clothing  of  the  men  is  of  such  a 
nature  as  to  prevent  the  contact  of  the  white  lead 
with  the  skin. 

From  what  precedes,  we  see  that  MM.  Lefevre  & 
Co.  have  taken  all  possible  precautions  for  protect- 
ing their  men  from  lead  diseases,  which  are  always 
dangerous  and  sometimes  mortal.  They  have  im- 
proved the  operations  of  casting  the  lead,  taking 
the  beds  apart,  separating  the  white  lead  from  the 
spirals,  grinding  the  white  lead  in  water  or  oil,  filling 
and  emptying  the  drying  pots,  dry  grinding,  and  sift- 
ing and  packing. 


154 


MANUFACTURE  OF  COLORS. 


C.  Safe  Apparatus  of  Mr.  Ozouf. 

Mr.  G.  H.  Ozouf,  to  whom  we  owe  several  ingeni- 
ous apparatuses  for  the  manufacture  of  gaseous 
waters,  has  invented,  for  the  preparation  of  white 
lead  by  the  Thenard  process,  an  apparatus  which 
rapidly  combines  the  carbonic  acid  with  the  acetate 
of  lead  in  a  closed  vessel,  into  which  both  are  pumped 
by  steam-power.  Under  pressure,  the  combination  is 
said  to  be  instantaneous,  and  there  is  produced  a 
white  lead  of  excellent  qualtity,  which  needs  but  to 
be  separated  and  dried.  The  description  of  this  in- 
teresting apparatus  is  found  in  the  TecJmologiste,  vol. 
xxii.  p.  519,  year  1861. 

D.  J.  Poelmann's  Machine  for  Separating  the  White 
Lead  from  the  Metal. 

Mr.  J.  Poelmann,  manufacturer  of  white  lead,  has 
also  endeavored  to  render  the  operations  less  unhealthy 
by  inventing  a  machine  for  separating  the  white  lead 
from  the  non-corroded  parts  of  the  coils  or  buckles. 

Figs.  33  and  31  represent  two  vertical  sections  of 
the  apparatus.  A  is  the  ground-floor  of  the  works,  b 
that  of  the  second  story,  and  c  that  of  the  third,  d, 
under  the  roof.  E,  box  to  hold  the  corroded  lead  before 
the  white  lead  is  separated,  f,  crank  driving  the 
gearing  p  p,  which  carries  the  box.  g,  wooden  ladder 
with  iron  rails  fixed  upon,  h  h,  pulleys,  carrying  the 
cord  attached  to  the  box  e.  k,  trough  delivering  the 
material  to  the  metallic  sieve  l.  m,  reservoir  for  the 
sifted  white  lead,  q,  small  car  upon  which  the  box 
E  is  fixed.  R,  latticed  loft  on  the  roof  for  ventilation, 
s,  draw  beam  for  opening  the  trap-door  i  of  the 
trough  K,  when  the  box  empties  itself  of  its  contents. 


WHITE  COLORS.  155 
Fig.  33. 


The  metallic  lead,  separated  from  the  white  scales, 
is  received  into  a  separate  box,  tightly  closed. 

E.  Precautions  taken  to  render  the  Manufacture  of  White  Lead 
less  unhealthy. 

In  the  examination  made  by  the  delegates  of  the 
Societe  d'Encouragement,  of  the  manufacture  of  white 
lead  at  Portillon,  near  Tours,  and  which  we  have 
already  described,  the  salubrity  of  the  processes  was 


156 


MANUFACTURE  OF  COLORS. 


Fig  34. 


especially  considered.  The  conclusions  of  their  report 
may  be  found  interesting. 

1.  The  works  are  well  adapted  for  this  manufacture, 
and  the  calcining  furnaces,  being  built  in  the  rock, 
preserve  their  heat. 

2.  All  possible  precautions  have  been  taken  for 
saving  the  men  from  the  toxical  action  of  the  lead 
pi'eparations. 


WHITE  COLORS. 


157 


3.  The  workshops  are  well  ventilated,  and  supplied 
with  railroads,  hoists,  and  other  labor-saving  appli- 
ances. 

4.  The  men  are  obliged  to  dress  in  a  complete  set 
of  working  clothes,  which  are  furnished,  washed,  and 
kept  in  order  at  the  expense  of  the  administration. 
There  are  hot  baths  in  the  works. 

5.  A  doctor,  paid  by  the  direction,  gives  the  neces- 
sary medical  care  to  the  sick,  and  every  week  makes 
a  general  inspection  at  the  works.  Thus,  a  beginning 
of  lead  disease  is  prevented  from  becoming  dangerous 
by  suitable  regimen. 

6.  Lastly,  we  consider  that  the  manufacture  of 
white  lead  at  the  works  of  MM.  Lallu  &  Delaunay  is 
as  harmless  as  practicable,  and  that  every  precaution 
has  been  taken  to  prevent  the  contact  of  poisonous 
substances.  Mechanical  has  been  substituted  for 
hand  work  wherever  it  has  been  possible;  and  where 
manual  labor  cannot  be  replaced  there  is  no  danger. 

We  have  had  the  pleasure  of  seeing  that  a  complete 
suit  of  working  clothes  was  furnished  by  the  direction 
to  the  men,  and  that  they  could  not  enter  the  work- 
rooms without  them.  At  the  end  of  the  day,  and 
before  getting  their  own  clothes,  the  men  have  a 
thorough  washing  with  soap  and  water.  Besides  all 
these  precautions,  all  the  men  are  examined  every 
week  by  a  doctor,  who  frequently  orders  medicated 
baths  prepared  in  the  works. 

We  have  also  seen  with  great  satisfaction  that  the 
manufacture  of  white  lead  ground  in  oil  is  daily  in- 
creasing at  Portillon.  When  its  employment  shall 
become  general,  and  no  lump  white  lead  is  sold,  we 
may  rely  on  a  termination  being  put  to  the  diseases 
due  to  white  lead. 


158 


MANUFACTURE  OF  COLORS. 


§  3.  White  of  haste  chloride  of  lead. 

For  some  time  past  the  effort  has  been  made  to 
replace  white  lead  or  carbonate  of  lead  by  a  basic 
chloride  of  lead,  which  is  mnch  less  soluble  in  water 
than  the  neutral  chloride.  Being  uncrystalline,  it 
possesses  great  body  or  covering  power. 

According  to  Mr.  L.  Brumlen,  of  New  York,  the 
lead  is  finely  granulated  by  passing  it  through  metallic 
sieves,  and  then  put  into  three  wooden  tubs  1.50 
metre  in  diameter  and  0.60  deep,  which  are  disposed 
so  as  to  empty  their  contents  one  into  the  other  by 
opening  spigots  placed  near  their  bottoms.  The 
top  vessel  is  filled  with  vinegar  (one  litre  of  which 
saturates  350  grammes  of  carbonate  of  soda)  or  with 
a  solution  of  neutral  acetate  of  lead  holding  a  little 
over  5  per  cent,  of  it. 

The  lead  which  has  been  thus  moistened  becomes 
rapidly  oxidized,  and  there  is  formed  a  neutral  acetate 
of  lead.  By  repeating  the  operation  the  basic  acetate 
is  obtained,  and  this  will  be  the  more  readily  pro- 
duced if  the  solution  already  contains  the  neutral 
acetate.  Up  to  this  point  the  process  does  not  present 
anything  very  new,  since  it  is  generally  employed 
for  preparing  neutral  acetates.  The  same  person 
also  states  that  litharge  may  just  as  well  be  dissolved 
in  acetic  acid. 

The  solution  of  acetate  of  lead  is  precipitated  in 
the  state  of  neutral  chloride  by  hydrochloric  acid — 
the  clear  liquid  and  the  washings  are  used  again  as 
acetic  acid.  The  neutral  chloride  of  lead  is  then 
digested  with  basic  acetate  of  lead  until  it  has  ex- 
tracted sufficient  lead  from  the  latter  to  become  basic. 
The  clear  liquor  is  decanted,  and  contains  a  neutral 


WHITE  COLOES. 


159 


acetate  of  lead.  The  precipitate  of  basic  chloride  of 
lead  is  washed  and  dried. 

The  solution  of  neutral  acetate  of  lead  of  the  second 
operation  is  employed  for  the  preparation  of  the  basic 
acetate.  Therefore,  there  is  very  little  waste  of  acetic 
acid,  which  is  the  costly  material. 

§  4.  Wliite  of  sulphite  of  lead. 

Carbonate  of  lead  is  not  the  only  salt  of  this  metal 
which  will  furnish  a  white  pigment,  and  several 
attempts  have  been  made  to  substitute  other  salts  for 
the  carbonate. 

Sulphite  of  lead  is  a  white  and  insoluble  powder, 
which  possesses  body  and  does  not  blacken  by  the 
contact  of  sulphuretted  hydrogen.  Mr.  Scoffern,  who 
has  proposed  its  employment,  says  that  it  is  obtained 
in  the  following  manner:  Sulphurous  acid  is  prepared 
by  heating  sawdust  with  concentrated  sulphuric  acid, 
and  the  gas  is  passed  through  a  solution  of  basic 
acetate  of  lead.  There  is  formed  a  precipitate  of  sul- 
phite of  lead,  and  the  liquor  is  a  solution  of  neutral 
acetate  which  may  be  rendered  basic  by  boiling  it 
with  litharge,  as  in  the  Th6nard  process 

§  5.  White  of  tung state  of  lead. 

Large  quantities  of  tungstate  of  soda  are  employed 
in  English  dye  works  as  a  mordant  substitute  for  tin 
salts.  50  kilogrammes  of  tunstate  of  soda  are  dis- 
solved in  the  smallest  possible  quantity  of  boiling 
water,  and  another  hot  and  concentrated  solution  of 
acetate  of  lead  is  poured  into  the  former  as  long  as  a 
precipitation  takes  place.  After  settling,  the  liquor 
is  decanted,  and  the  tungstate  of  lead  is  drained  and 
washed.    The  liquors  contain  the  soluble  acetate  of 


160 


MANUFACTURE  OF  COLORS. 


soda,  but  the  basic  salt  of  lead  is  transformed  into  the 
acid  tungstate  by  a  treatment  with  nitric  acid  (sp.  gr. 
1.3)  or  acetic  acid  (sp.  gr.  1.05),  diluted  with  their 
volume  of  water.  The  mixture  is  stirred  now  and 
then,  and  when  the  precipitate  has  acquired  a  certain 
consistency,  the  liquor  is  decanted,  and  the  tungstate 
is  washed  with  cold  water.  After  draining  upon 
cloth  filters  it  is  dried  upon  porous  stones,  which  are 
heated  at  a  moderate  temperature  in  stove  rooms. 
The  decanted  liquors  or  washings  are  saved  on 
account  of  the  oxide  of  lead  they  hold. 

This  process,  as  well  as  the  two  following,  has  been 
indicated  by  Mr.  Spilsburg.  The  pigments  obtained 
are  costly,  do  not  cover  better  than  white  lead,  and 
are  open  to  the  same  inconveniences. 

§  6.  Antimonite  of  lead. 

If  we  boil  fifty  parts  of  metallic  antimony  with 
twenty  parts  of  concentrated  sulphuric  acid,  sulphu- 
rous acid  is  disengaged,  and  there  remains  a  white 
saline  mass,  which  is  a  sulphate  of  antimony.  This 
salt  is  heated  until  it  no  longer  produces  acid  fumes, 
and  is  then  transformed  into  antimonious  acid  b}^  a 
calcination  in  a  crucible  with  twenty-one  parts  of  dry 
carbonate  of  soda.  The  fused  substance  is  boiled  in 
water,  and  the  solution  is  decomposed  by  neutral 
acetate  of  lead.  The  precipitate  is  a  heavy  antimo- 
nite of  lead,  which  is  separated  from  the  liquor  hold- 
ing acetate  of  soda.  The  pigment  is  collected  upon 
filtering  cloths,  and  when  it  has  become  pasty,  it  is 
formed  into  lumps  which  are  dried  upon  bricks  in  a 
stove  room,  at  the  temperature  of  60°  C. 


WHITE  COLOKS. 


161 


§  7.  Antimoniate  of  lead, 

A  mixture  of  one  part  of  sulphide  of  antimony  and 
five  parts  of  nitrate  of  potassa,  is  deflagrated  in  a  red- 
hot  crucible,  or  upon  the  bed  of  a  reverberatory  fur- 
nace. The  calcined  product  is  almost  entirely  soluble 
in  boiling  water,  and  the  solution  is  decomposed  by 
another  of  neutral  acetate  of  lead.  The  precipitate  is 
separated,  washed,  and  dried  in  a  stove-room.  This 
antimoniate,  when  pure,  is  white,  heavy,  and  possesses 
a  certain  body. 

§  8.  Antimony  whites. 
Many  attempts  have  been  made  for  employing  the 
oxide  of  antimony  in  painting,  but  they  seem  to  have 
met  with  but  little  success,  although  the  antimony 
white  possesses  many  good  qualities.  It  stands  water, 
is  as  opaque  as  white  lead,  is  scarcely  acted  upon  by 
sulphurous  fumes  or  sulphuretted  hydrogen,  and  it 
produces  durable  painting  especially  suitable  for  out- 
side work. 

1st.  Antimony  White  of  MM.  Bobierre,  Euolz^  and  Rousseau. 

It  is  intended  by  this  process  to  substitute  for 
white  lead  a  substance  which  contains  no  lead,  is  not 
so  dangerous  to  the  health  of  workmen,  and  which 
may  be  obtained  at  a  price  equal  or  less  than  that  of 
white  lead. 

After  many  experiments,  these  manufacturers  gave 
the  preference  to  the  oxide  of  antimony,  which  may 
be  prepared  by  known  processes ;  nevertheless,  they 
consider  that  the  following  method  is  more  econom- 
ical : — 

"In  an  apparatus,  which  may  be  modified  in  many 
ways,  a  brick  oven  or  a  cast-iron  furnace  for  instance, 
11 


162 


MANUFACTURE  OF  COLORS. 


there  are  made  to  play  on  the  heated  surflice  of  sul- 
phide of  antimony,  a  draft  of  air  and  a  jet  of  steam 
which  may  he  regulated  for  each  kind  of  sulphide 
employed.  All  the  sulphur  escapes  in  the  state  of 
sulphurous  acid,  which  may  he  saved,  and  the  anti- 
mony is  converted  into  the  white  oxide,  which  is 
collected  in  receivers  placed  at  the  end  of  the  heating 
apparatus. 

"  This  product  may  also  he  prepared  in  an  ordinary 
roasting  furnace,  but  it  is  not  so  comminuted  as  that 
obtained  with  the  aid  of  steam.  Oxide  of  zinc,  other 
white  oxides,  and  certain  compounds  prepared  in  a 
similar  manner,  acquire  peculiar  properties  which 
were,  until  now,  unknown. 

"  The  product  thus  prepared  may  be  ground  im- 
mediately in  oil,  without  passing  through  the  opera- 
tions of  drying,  pulverizing,  sifting,  etc. 

"Considering  the  abundance  and  the  cheapness  of 
the  natural  sulphide  of  antimony,  the  white  oxide 
may  be  obtained  at  a  cheaper  rate  than  white  lead. 
Moreover,  its  covering  power  is  at  least  twice  that  of 
the  best  white  lead." 

2d.  Antimony  White  of  MM.  Valle  and  Barreswill. 

Here  is  the  process  of  MM.  Yalle  and  Barreswill, 
as  explained  by  themselves  : — 

"We  wish  to  record  the  results  which  we  have 
obtained  in  our  study  of  various  chemical  compounds, 
intended  as  substitutes  for  white  lead  in  oil  painting. 

"  Many  experiments  have  already  been  made  on 
this  subject,  and  are  found  in  the  treatise  on  painting 
by  Mr.  de  Montabert.  It  results  from  our  own  re- 
searches :  1st,  that  several  lead  compounds,  other 
than  the  carbonate,  may  be  used  the  same  as  white 


WHITE  COLORS. 


163 


lead.  2d,  that  antimony,  after  lead  and  bismuth,  is 
the  metal  which  furnishes  white  pigments  with  the 
best  covering  power.  This  observation,  mentioned 
by  Mr.  de  Montabert,  has  since  been  pointed  out 
anew  by  Mr  de  Euolz  (Technologiste,  5th  year,  page 
155). 

"  The  same  as  with  white  leads,  the  bodj^  or  cover- 
ing power  of  antimony  whites  varies  with  their  mode 
of  preparation. 

"  Mr.  de  Montabert  states  his  preference  for  the 
oxide  of  antimony ;  ours  is  for  Algaroth  powder, 
which  appears  to  us  to  possess  properties  similar  to 
those  of  white  lead.  However,  we  reserve  for  our- 
selves the  right  of  employing  the  oxide  (prepared 
from  the  oxichloride  and  carbonate  of  soda)  sublimed 
or  not.  Here  is  the  mode  of  preparation  of  this  new 
white : — 

"  The  Algaroth  powder  is  obtained  by  the  treat- 
ment of  the  sulphide  of  antimony  by  hydrochloric 
acid.  The  sulphuretted  hydrogen  is  made  to  burn, 
and  the  sulphurous  acid  produced  is  employed  in  lead 
chambers  for  the  manufacture  of  sulphuric  acid. 

"The  clear  and  settled  chloride  of  antimony  is 
decomposed  by  water. 

"  The  hydrochloric  acid  resulting  from  this  decom- 
position, and  which  still  retains  small  proportions  of 
antimony,  is  used  for  condensing  hydrochloric  acid 
gas,  or  for  separating  the  gelatin  from  bones. 

"We  also  manufacture  the  new  antimony  white  by 
treating  with  hydrochloric  acid,  either  the  residue  of 
antimony  ore  calcined  at  a  low  temperature,  or  the 
product  of  the  action  of  sulphuric  acid  upon  the 
sulphide  of  antimony. 

"The  sulphurous  acid  resulting  from  the  treatment 


164 


MA^^^UFACTURE  OF  COLORS. 


of  the  antimony  ore  is  employed,  either  for  the  manu- 
facture of  sulphuric  acid,  or  for  that  of  sulphurous 
acid  and  sulphites  ;  in  fact  for  all  the  uses  of  sulphu- 
rous acid. 

"  For  the  manufacture  of  antimony  whites.  Alga- 
roth  powder,  and  oxide  by  the  dry  or  by  the  wet  way, 
we  make  no  difference  whether  the  sulphide  of  anti- 
mony contains  iron  or  not.'' 

3d.  Antimony  White  of  MM,  Hallelt  and  Stenhouse, 

MM.  G.  Hallett  and  J.  Stenhouse  employ  a  natural 
oxide  of  antimony,  or  an  ore  where  the  sulphide  and 
the  oxide  are  associated  together.  The  mineral  is 
finely  pulverized,  and  separated  from  its  gangue  by 
washing  and  mechanical  processes.  The  heavy  me- 
tallic portions  are  calcined  in  a  reverberatory  furnace, 
and  the  sulphur  is  driven  off  as  sulphurous  acid. 
The  residue  is  mostly  antimonious  acid,  which,  after 
being  further  powdered,  is  mixed  with  oil  or  varnish. 

The  product  is  often  contaminated  with  small  pro- 
portions of  lead,  coi^per,  or  iron,  which  diminish  its 
whiteness.  In  such  a  case  it  is  reserved  for  inferioi* 
painting. 

The  pure  antimony  white  is  less  affected  by  sul- 
phuretted hydrogen  than  white  lead.  It  possesses 
more  body  than  zinc  white,  but  less  than  white  lead. 

§  9.  Zinc  white. 

For  a  century  the  unalterability  of  zinc  white  was 
known  by  chemists,  and  Courtois,  of  the  Laboratoi-y 
of  Dijon,  mentioned  it  in  1770  to  the  academy  of  that 
city.  Three  years  later  Guy  ton  de  Morveau  pub- 
lished a  memoir  on  the  same  subject,  which  was 
reprinted  in  the  Encydopedie  Methodique  des  Arts  ei 


WHITE  COLORS. 


165 


Metiei^s^  then  published.  After  several  experiments, 
this  learned  chemist  proved,  in  the  presence  of  the 
Prince  de  Conde,  that  painting  done  with  tartrate 
of  lime,  tin  white,  and  zinc  white,  and  exposed  to  the 
contact  of  sulphuretted  hydrogen,  was  not  changed 
in  color. 

In  1796,  Mr.  Atkinson,  of  Harrington,  took  out  a 
patent  for  the  application  of  zinc  white,  and  Guy  ton 
de  Morveau,  in  the  Annales  des  Arts  et  Manufactures, 
claimed  for  France  the  priority  of  invention,  since,  in 
1781,  Courtois  had  begun  the  manufacture  of  zinc 
white  on  a  large  scale,  and  that  stores  existed  at 
Paris  and  at  Dijon  for  the  sale  of  that  material. 
Moreover,  zinc  white  was  already  employed  in  France 
for  artistic  paintings,  for  mixing  with  other  colors,  etc. 

The  inside  paintings  of  the  man-of-war  le  Languedoc 
having  been  done  with  zinc  white,  in  1786,  a  commis- 
sion for  its  examination  made  the  following  report : — 

I.  The  painting  with  zinc  white  is  handsome,  but 
not  so  bright  as  that  with  white  lead ; 

II.  The  smell  of  the  fresh  zinc  paint  is  not  so 
^ti'ong  or  disagreeable  as  that  of  white  lead ; 

III.  The  zinc  paint  took  six  days  to  dry,  whereas 
four  days  were  sufficient  for  white  lead; 

IV.  250  grammes  of  zinc  white  and  the  same  quan- 
tity of  nut  oil  were  sufficient  to  cover  a  surface  of  a 
little  above  3.80  square  metres,  etc. 

A  copy  of  this  report  being  transmitted  to  the 
Marshal  de  Castrie,  then  Secretary  of  the  ^avy,  he 
recommended  zinc  paint  for  the  insides  of  ships. 

In  a  report  made  at  the  Institut,  in  1808,  by  Four- 
croy,  Bertholet,  and  Vauquelin,  we  remark  the  follow- 
ing passage:  "Among  the  products  manufactured  by 
Mr.  MoUerat  there  is  a  zinc  white,  the  use  of  which 


1G6 


MANUFACTURE  OF  COLORS. 


should  be  strongly  recommended.  Its  defects  are  so 
slight  in  comparison  with  those  of  white  lead,  that  it 
should  be  adopted,  at  least  in  house  painting.  Be- 
sides its  salubrity,  it  gives  purer  colors ;  and,  if  its 
brightness  is  less  at  the  beginning,  it  does  not  darken. 
With  equal  Aveights  it  covers  a  larger  surface  than 
carbonate  of  lead,  and,  although  it  is  more  dry  under 
the  brush,  this  is  easily  remedied  by  charging  the 
brushes  oftener,  or  giving  another  coat." 

Lastly,  in  September,  1844,  Mr.  Mathieu  sent  to 
the  Academy  of  Sciences  a  memoir  on  the  oxide  of 
zinc^  in  which  he  says  that  he  obtains  that  product  in 
a  state  of  great  purity,  and  by  a  much  cheaper  pro- 
cess than  those  then  followed.  Mr.  Mathieu  does  not 
indicate  the  process,  but  he  insists  on  the  economy 
of  the  new  method,  and  on  the  futiu'e  of  the  oxide  of 
zinc,  which  ought  to  take  the  place  of  white  lead  in 
the  majority  of  cases.  Moreover,  it  does  not  compro- 
mise the  health  of  the  men  employed  in  its  manu- 
facture. 

How  is  it  then  that,  notwithstanding  all  these  re- 
searches, successful  trials,  and  honorable  testimonials, 
the  zinc  w^hite  has  not  reached  the  place  it  ought  to 
occupy  in  the  arts  ? 

A  contractor  in  painting  work  at  Paris,  Mr.  Le- 
claire,  after  acquiring  a  full  knowledge  of  what  had 
been  done  before  him,  has  established  at  Courcelles, 
near  the  Seine,  large  works  for  the  manufacture  of 
zinc  white,  and  has  added  several  important  improve- 
ments. 

1st.  Manufacture  of  Zinc  White ^  by  Mr.  Leclaire. 

Mr.  Leclaire  has  established  in  his  works  a  Silesian 
furnace  with  ten  retorts.   An  arrangement  of  scrapers 


WHITE  COLORS. 


167 


keeps  the  months  of  the  retoi-ts  constantly  open,  and 
in  front  of  them  is  a  very  small  chamber,  the  floor  of 
which  is  movable,  and  with  a  door  which  opens  in  the 
room  where  the  furnace  is.  The  top  of  this  small 
chamber  is  connected  with  the  upper  part  of  the  con- 
densing rooms,  which  stand  on  the  right  and  left  of 
the  furnace,  and  are  deeper  than  the  level  of  the  fur- 
nace floor. 

A  powerful  draft  exists  at  the  end  of  a  series  of 
cloth  drums  which  receive  the  last  particles  of  oxide 
of  zinc.  The  floors  of  the  condensing  rooms  are  pro- 
vided with  hoppers,  through  which  the  oxide  falls 
into  the  barrels. 

Manufacture, — "When  the  furnace  is  at  the  proper 
temperature,  the  door  of  the  small  chamber  is  opened, 
and  the  zinc  is  introduced  into  the  retort.  The  door 
is  then  closed  and  luted,  and  the  movable  floor  lifted. 
The  combustion  of  the  zinc  begins  immediately,  and 
ceases  only  when  all  the  metal  is  burned  out,  that  is, 
oxidized  by  the  oxygen  of  the  air  which  comes  through 
the  lower  part  of  the  chamber.  The  oxide  of  zinc, 
according  to  its  degree  of  lightness,  is  carried  to  a 
greater  or  less  distance,  and  is  collected  in  the  hop- 
pers placed  at  the  bases  of  the  different  condensing 
apparatuses. 

With  two  furnaces  it  is  possible  to  produce  every 
day  6000  kilogrammes  of  oxide  of  zinc,  which  is  sold 
at  from  70  to  75  francs  per  100  kilogrammes. 

There  is  no  more  difficulty  in  painting  with  zinc 
white  than  with  white  lead.  Zinc  white  may  be  per- 
fectly well  mixed  with  oil,  without  grinding,  by  ope- 
rating as  follows :  The  zinc  white,  oil,  and  essence  of 
turpentine  are  mixed  together,  and  allowed  to  stand 


168 


MANUFACTURE  OF  COLORS. 


for  about  six  minutes ;  the  whole  is  then  stirred  with 
a  brush  and  passed  through  a  sieve. 

Zinc  white,  whether  alone  or  mixed  with  other  pig- 
ments, is  used  for  oil  and  water  colors,  for  varnish, 
and  for  distemper  painting,  etc.  Zinc  white  may 
also  be  used  :  I.  In  the  manufacture  of  smooth  papers 
and  of  visiting  cards  as  a  substitute  for  white  lead  ; 
II.  As  a  component  part  of  mastics  for  keeping  tight 
the  joints  of  steam  engines  ;  III.  For  a  face  powder, 
colored  with  a  small  pi'oportion  of  carmine;  IV.  And 
in  the  manufacture  of  Brussels  laces. 

Zinc  white  may  be  mixed  with  various  pigments 
possessing  durability,  such  as  the  oxides  of  iron, 
charcoal,  oxide  of  manganese,  ultramarine,  etc.  etc., 
and  will  then  furnish  colors,  the  tones  of  which  will 
remain  permanent,  and  this  is  a  great  advantage  in 
painting. 

The  white  or  gray  pigments  prepared  with  the 
zinc  oxide  are  not,  like  those  with  a  basis  of  white 
lead,  altered  by  hydrosulphuretted  fumes.  Repeated 
trials  have  been  made  which  prove  that  painting  with 
zinc  oxide  stands  well  in  privies,  and  in  those  places 
where  Bareges  (sulphur)  baths  are  administered. 

An  experiment  has  also  demonstrated  that  zinc 
paints  may  be  employed,  like  red  lead  and  orange 
mineral,  for  preserving  iron  from  oxidation. 

Mr.  Leclaire  has  indicated  a  method  of  preparing 
drying  oil  without  lead,  but  with  the  peroxide  of 
manganese.  200  parts  of  boiled  linseed  oil  and  10 
parts  of  peroxide  of  manganese  are  boiled  together 
for  six  and  eight  hours,  and  the  mixture  is  frequently 
stirred.  After  cooling  and  filtration,  the  oil  has 
become  a  good  dryer. 

Lastly,  Mr.  Leclaire  has  also  prepared  variously 


WHITE  COLORS. 


1(39 


colored  pigments,  with  zinc  as  a  basis,  for  artists  and 
honse  painters.    These  pigments  are  : — 

1.  Oold  hutt  'Ti  (houtoii  d'or)  yellow  ;  2.  Lemon  yel- 
low ;  3.  Pale  yellow;  4.  Baryta  yellow;  5.  DarTc 
English  green;  6.  Light  English  green;  7.  Milori 
green  ;  8.  Oreen  earth. 

We  find  in  the  Technologiste  the  following  descrip- 
tion of  a  process  for  the  manufactnre  of  the  oxide  of 
zinc : — 

Zinc  white  may  be  prepared  by  the  distillation  of 
the  zinc  ore  or  of  the  metal  in  special  furnaces. 


Fig.  36. 


Description  of  the  apparatus, — Fig.  35  is  a  hori- 
zontal section  of  a  glass  furnace,  with  certain  modifi- 
cations which  will  be  explained 
further  on,  and  with  the  additional 
fixtures  necessary  for  the  manu- 
facture and  the  condensation  of 
zinc  white. 

Fig.  36  is  a  transverse  section  of 
the  furnace. 

Fig.  37  is  a  longitudinal  section. 

A,  door  of  the  furnace,    b,  fire- 
place,   c  c,  retorts  made  of  clay  or 
of  any  other  substance  able  to  stand  a  high  tempera- 
ture.   There  are  five  retorts  on  each  side,  but  the 


170 


MANUFACTURE  OF  COLORS. 


number  may  vary,  d  d,  openings  of  the  retorts, 
through  which  the  products  of  the  distillation  escape. 
F  F,  iron  rods  or  scrapers  for  keeping  the  mouths  of 
the  retorts  open,  e  e,  horizontal  bar  to  which  the 
scrapers  are  attached.  By  pushing  it  backwards  and 
forwards,  the  scrapers  do  their  work.  Motion  is  im- 
parted by  hand  or  by  power,  g  g,  hoppers  which 
receive  the  heavy  portions  of  the  calcined  zinc.  They 
are  placed  below  the  mouths  of  the  retorts,  and  their 
lower  parts  are  connected  by  short  pipes  with  a 
general  trough  a\  which  delivers  the  products  into 
the  receiver 

It  is  well  understood  that  these  hoppers  receive 
only  the  heavy  portions  of  the  distilled  products,  or 
the  scrapings  from  the  mouths  of  the  retorts,  the 
weight  of  which  is  too  considerable  to  be  carried  by 
the  draft  into  the  oxidizing  chamber. 


Fig.  37. 


H  is  a  small  iron  cage  which  isolates  each  retort 
from  the  others,  and  which  stands  upon  a  low  wall. 
It  may  be  moved  or  shifted  by  means  of  a  crane  or  of 
rollers.  The  open  part  of  these  cages  is  in  front  of 
the  mouths  of  the  retorts,  so  that  the  distilled  products 
may  pass  from  the  cage  into  the  oxidizing  chambers 


WHITE  COLORS. 


171 


and  condensers.  In  Fig.  35  some  of  these  cages 
are  represented,  the  others  are  not.  Their  back 
part  may  be  opened  or  closed,  as  desired,  j  is  an 
opening  on  the  floor  K,  which  is  closed  with  a  hinged 
trap  door,  raised  or  lowered  by  means  of  a  chain  i, 
one  end  of  which  passes  through  the  partition,  so  as 
to  operate  without  opening  the  cage.  Other  ways  of 
moving  this  trap  door  may  be  devised. 

The  arrangements  h,  i,  j  could  be  adapted  to  the 
furnaces  where  zinc  is  smelted.  There  is  always  a 
certain  proportion  of  zinc  oxide  formed  which  is  lost, 
and  which  could  be  saved  in  the  above-described 
manner,  or  by  closing  with  a  cloth  the  spiace  where 
the  zinc  is  collected.  If  the  iron  cage  or  chamber  be 
used,  a  small  opening  is  made  on  the  partition  i, 
which  is  closed  with  a  glass,  so  as  to  allow  of  the 
watching  of  the  distillation.  The  same  result  will  be 
obtained  by  fixing  iron  plates  on  each  side  of  the 
opening  of  the  retorts.  Another  movable  plate  will 
be  used  as  a  cover. 

K,  floor  carrying  the  cages  H,  and  separating  this 
part  of  the  apparatus  from  the  oxidizing  chamber. 
The  air  drafts  may  be  introduced  into  the  chamber 
having  K  for  the  floor,  or  through  the  floor  itself, 
which,  then,  should  be  hollow.  Fresh  air  is  neces- 
sary, in  order  to  lower  the  temperature  of  the  cham- 
ber above  the  floor. 

L,  hot  air  pipe  communicating  with  the  hoppers 
G  G,  and  carrying  away  the  white  oxide  into  the 
oxidizing  chamber.  Instead  of  hot  air,  cold  air  may 
be  passed  through  the  cages  h,  or,  if  it  be  thought 
desirable,  a  mixture  of  cold  and  hot  air  may  be  intro- 
duced. 

M,  oxidizing  room,  where  the  metallic  vapors  are 


172 


MANUFACTURE  OF  COLORS. 


oxidized  by  atmospheric  air,  as  soon  as  they  escape 
fi-om  the  retorts,  li^,  portion  of  the  oxidizing  chamber, 
where  there  are  cloths  for  sifting  the  products.  The 
lower  part  is  hopper  shaped,  and  conducts  the  oxide 
of  zinc  into  receivers  below.  There  are  valves,  regis- 
ters, etc.,  for  letting  the  product  in  or  out. 

The  whole  of  the  product  may  be  collected  with- 
out loss,  by  means  of  properly  arranged  vessels  or 
receivers  filled  with  water,  and  provided  with  two 
tubes.  One  of  the  latter  communicates  with  the 
oxidizing  room,  and  dips,  at  the  other  end,  into  the 
water  of  the  receiver.  It  conducts  the  zinc  white 
from  the  oxidizing  room  into  the  receiver.  The  end 
of  the  other  tube  does  not  dip  into  water,  but  takes  in 
the  air  of  the  receiver  and  produces  a  vacuum  in  the 
other  tube,  thus  forcing  the  descent  of  the  products, 
o,  o  are  the  receivers  for  the  oxide,  p,  p,  partitions 
of  metallic  wire,  or  cloth,  for  allowing  the  air  to  pass 
through,  and  for  sifting  and  retaining  the  products. 
Q,  exhaust  tube  for  moving  the  air  through  the  sifting 
surfaces,  and  attracting  the  products  towards  the 
receivers. 

R  is  another  tube  or  hood  placed  on  top  of  the 
opening  of  each  retort,  and  intended  for  the  escape  of 
the  volatilized  products,  when  the  charge  is  put  in, 
and  when  the  communication  with  the  oxidizing  room 
is  closed  by  the  trap-door  j.  The  hood  r  carries  the 
volatilized  products,  by  suitable  conducts  not  seen  in 
the  figure,  into  the  oxidizing  room,  or  into  a  special 
condensing  apparatus.  A  draft  may  be  produced, 
either  by  heating  the  hood,  or  by  an  exhauster.  This 
hood  is  closed  during  the  distillation,  as  long  as  the 
metallic  vapors  pass  directly  into  the  oxidizing  cham- 


WHITE  COLORS. 


173 


ber.  In  this  case,  the  vacuum  or  exhaust  is  produced 
by  the  lost  heat  of  the  furnace. 

In  the  preceding  arrangement,  the  retorts  are  sep- 
arated each  from  the  other,  and  we  readily  understand 
that  this  result  may  be  arrived  at  by  other  analogous 
methods.  For  instance,  the  floor  k  may  be  disposed 
so  as  to  be  raised  or  lowered  at  will,  in  order  to  sep- 
arate the  retorts  one  from  another.  It  may  be  divided 
into  as  many  sections  as  there  are  retorts,  so  that,  by 
raising  or  lowering  one  of  them,  the  communication 
with  the  oxidizing  room  may  be  established  or  closed. 


Fig.  38. 


The  retorts  may  also  be  separated  by  partitions  and 
rendered  independent  of  each  other.     The  hood  r 


Fig.  39. 


may  have  such  dimensions  and  exhausting  power  as 
to  carry  all  of  the  products  into  the  condensing  rooms. 

Fig.  38  represents  a  horizontal  section  of  another 
furnace  for  the  manufacture  of  zinc  white. 


174 


MA^^^UFACTURE  OF  COLORS. 


Fig.  39  is  a  longitudinal  section. 
Fig.  40  is  a  transverse  section. 
This  fu  rnace  is  closed  on  top,  either  by  a  cover 
which  may  be  moved  for  charging  the  retorts,  or  by 

a  hopper  filled  with  the  sub- 

Fio-.  40. 

Stances  for  the  operation.  It 
could  be  hermetically  closed  on 
top,  and  opened  on  the  sides  for 
charging.  Lastly,  the  materials 
may  be  introduced  through  the 
opening  b,  and  in  this  case,  an 
inclined  plane  is  so  disposed  as 
to  receive  the  materials. 

All  these  dispositions,  and 
others,  are  well  known,  and  we  shall  only  examine 
the  principal  details. 

A,  air  furnace  of  proper  size,  b,  opening  through 
which  the  products  pass  into  the  oxidizing  room  c, 
which  is  arranged  as  in  the  preceding  figures.  Be- 
tween the  various  hoppers  of  the  oxidizing  room,  there 
are  metallic  or  cloth  sieves,  to  arrest  the  heavier  pro- 
ducts or  the  impurities  carried  away  through  b.  The 
oxide  of  zinc,  being  very  light  and  comminuted,  passes 
through  these  screens.  The  opening  b  may  be  pro- 
vided with  a  register  or  damper,  for  closing  the  com- 
munication between  the  furnace  and  the  oxidizing 
rooms,  whenever  the  circumstances  require  it. 

The  charging  hole  may  be  provided  with  a  hopper, 
or  any  other  apparatus  for  delivering  the  materials  as 
the  distillation  progresses.  Besides  the  current  of  air 
caused  by  the  draft  or  blast,  and  necessary  for  the 
combustion,  another  injection  of  air  could  be  made  to 
furnish  the  necessary  oxygen  to  the  vapors  of  zinc, 
either  in  the  furnace  or  in  the  flue  b. 


WHITE  COLORS. 


175 


The  furnace  may  be  circular  in  shape,  or  horizontal, 
or  more  or  less  inclined.  Instead  of  one  opening  b, 
several  may  be  made  at  different  heights,  even  near 
the  fireplace ;  in  which  case  the  products,  as  soon  as 
formed,  are  carried  directly  into  the  oxidization  room, 
without  being  obliged  to  pass  through  the  materials 
piled  above.  A  reverberatory  furnace  may  be  em- 
ployed, and  also  a  coke-oven ;  but  in  the  latter  case, 
there  should  be  a  fireplace  heating  the  furnace  by 
means  of  flues  circulating  under  the  hearth  or  sole, 
and  in  the  side  walls.  A  top  opening  will  be  used 
for  charging,  and  a  side  one  for  the  passage  of  the 
products  into  the  oxidizing  and  condensing  rooms. 


Fig.  41  is  a  horizontal  view  of  another  kind  of 
furnace  for  the  manufacture  of  oxide  of  zinc. 

Fig.  42  is  a  transverse  section. 

Fig.  43  is  a  longitudinal  section. 

We  see  that  this  furnace  consists  of  two  horizontal 
and  parallel  flues  or  retorts,  with  fireplaces  receiv- 
ing a  blast  of  air.  A  A,  flues  built  of  fire  bricks. 
B  B,  tuyeres  for  hot  or  cold  air  blast,  c,  lower  part 
of  the  fireplace,  where  the  cinders  and  ashes  are 
collected.  These  are  removed  now  and  then  through 
a  lower  opening.    But  if  large  ash  pits  J  J  are  left 


176 


MAXUFACTURE  OF  COLORS. 


in  the  brickwork,  the  part  c  is  closed  with  a  grate  or 
damper.  With  grate  bars  sufficiently  close  to  retain 
the  ore,  and  large  enough  to  let  the  cinders  fall  through, 
a  natural  draft  of  air  may  be  substituted  for  the  arti- 

Fig.  43. 


ficial  blast.  In  this  case,  the  proper  fluxes  should  be 
added  to  the  ore,  for  transforming  the  earthy  ^^arts 
into  fluid  cinders. 

D  D  are  fireplaces  opening  into  the  same  arched 
flue  F.  The  charge  of  ore  and  coke  is  piled  up  to  the 
level  a.    e  e,  brickwork  separating  the  fireplaces. 

The  air  may  be  admitted  into  the  flue  f,  either  by 
compression  or  exhaustion,  for  oxidizing  the  metallic 
vapors  and  carrying  them  into  the  condensing  rooms. 

At  each  end  of  the  flue  f,  there  are  dampers  g  g, 
establishing  the  communication  with  the  condensing 
or  collecting  rooms,  h  h  are  these  rooms,  which  are 
arranged  in  the  manner  previously  described.  In- 
stead of  two  rooms  only  one  may  be  used,  if  desired. 
Ill  are  the  openings  for  charging,  which  stand  im- 
mediately above  the  fireplaces.  They  are  closed  by 
a  tight  cover,  or  by  a  metallic  hopper  filled  with  the 
ore  mixture,  which  is  thus  dried. 

We  readily  see  that  this  apparatus  may  be  modified 
in  several  ways.   For  instance,  instead  of  two  series 


WHITE  COLORS. 


177 


of  tuyeres,  only  one,  or  a  greater  number,  may  be 
employed.  The  number  and  the  sizes  of  the  fireplaces 
may  vary.  The  brickwork  may  be  raised  still  higher, 
and  less  space  left  for  the  passage  of  the  air  and 
the  metallic  vajoors.  The  two  collecting  chambers 
may  be  replaced  by  one.  These  modifications  do 
not  change  the  principle  of  the  invention,  which 
consists  in  a  horizontal  tubular  flue,  connected  with 
one  or  several  fireplaces  using  a  natural  or  forced 
draft  of  air,  and  which  communicates  with  rooms  into 
which  the  products  of  the  combustion  are  driven  by 
exhaustion  or  by  compressed  air. 

Mode  of  operation. — 1.  With  the  retorts, — Ingots 
of  zinc  are  charged  into  the  retorts,  which  have 
been  previously  brought  to  a  white  heat.  As  soon  as 
the  whole  charge  is  in,  the  iron  cage  h  is  closed, 
and  the  trap-door  on  the  floor  is  lifted,  so  as  to 
put  the  retort  into  direct  communication  with  the 
oxidizing  room.  The  vapors  of  the  distilled  zinc 
become  oxidized  by  the  air,  and  the  white  oxide  is 
constantly  drawn  into  the  receiving  or  condensing 
room  by  the  vacuum  maintained  in  the  pipe  R.  The 
oxide  is  arrested  by  metallic  screens  which  allow 
of  the  passage  of  the  air,  and  falls  into  hoppers, 
which  deliver  it  into  the  receivers.  When  the  retort 
is  empty,  the  trap-door  is  closed,  the  damper  over 
the  hood  is  lifted,  and  a  new  charge  is  put  in,  and 
the  operation  continues  as  before. 

If  we  operate  with  a  zinc  ore,  or  an  oxide  of  this 
metal,  it  is  mixed  with  half  its  weight  of  charcoal, 
coke,  or  bituminous  coal,  as  is  done  in  the  ordinary 
treatment  of  zinc  ores. 

If  the  ore  is  a  blende,  that  is,  a  sulphuret,  it  is 
12 


178 


MANUFACTUKE  OF  COLORS. 


necessary  to  add  a  certain  proportion  of  peroxide  of 
manganese,  carbonate  of  lime,  or  oxide  of  iron,  in  the 
ratio  of  the  sulphur  contained  in  the  ore. 

2.  Air  furnace. — When  we  employ  the  air  furnace, 
the  charge  of  ore  is  mixed  with  the  above-mentioned 
substances,  and  with  a  certain  proportion  of  a  proper 
flux.  As  soon  as  the  zinc  becomes  separated  from 
the  foreign  substances  with  which  it  was  combined, 
its  vapors  are  rapidly  oxidized,  and  the  zinc  white  is 
collected  in  the  rooms  ah-eady  mentioned. 

3.  Beverheratory  furnace  or  coke  oven. — The  working 
of  the  i-everberatory  furnace  is  so  well  known,  that  it 
is  useless  to  describe  it  here.  The  mode  of  charging 
and  cleaning  it  is  the  same  as  with  other  ores.  This 
method,  however,  does  not  appear  so  advantageous  as 
the  others.  When  furnaces,  similar  to  coke  ovens, 
are  employed,  they  are  charged  while  very  hot  with 
metallic  zinc  or  its  oxides,  alone  or  mixed  with  coal. 
A  current  of  air  passes,  either  through  the  furnace, 
or  only  at  the  opening  through  which  the  metallic 
vapors  escape  to  go  into  the  collecting  room.  If  the 
metal  be  employed  with  this  apparatus,  or  any  similar 
one,  it  may  be  made  to  fall  by  drops  by  passing  it  in 
the  molten  state  through  a  metallic  sieve. 

4.  Horizontal  tubular  furnace. — After  the  furnace 
has  been  brought  up  to  the  proper  temperature  with 
bituminous  coal  or  coke,  the  mixture  of  ore  and  fuel 
is  thrown  in  through  the  openings  1 1 1,  with  a  certain 
proportion  of  aluminous  or  calcareous  flux  to  suit  the 
nature  of  the  gangue.  The  space  f  is  left  open. 
When  blende  is  used  without  previous  calcination, 
the  ore  is  mixed  with  peroxide  of  manganese,  car- 
bonate of  lime,  or  oxide  of  iron,  in  proportion  to  the 
sulphur  held  by  the  blende.    The  ore  is  decomposed. 


WHITE  COLORS. 


170 


and  the  metallic  vapors  are  oxidized  and  collected  in 
the  manner  previously  explained. 

Immediately  after  charging,  and  until  the  mass  is 
in  an  incandescent  state,  gases  and  solid  but  light 
substances  are  disengaged,  which,  if  received  in  the 
collecting  rooms,  would  impair  the  whiteness  of  the 
products.  This  is  the  reason  why  two  condensing 
rooms  are  employed,  one  on  each  side.  One  of  these 
rooms  receives  the  products  distilled  before  the  whole 
mass  is  in  the  incandescent  state,  and  the  other,  by  a 
change  of  dampers,  is  employed  for  the  pure  products. 
The  disposition  of  the  collecting  or  condensing  rooms 
is  common  to  all  the  various  processes. 


Fig.  44. 


Figs.  44,  45,  and  46  represent  a  furnace  built  in 
the  manner  of  those  employed  in  the  manufacture  of 
gas,  but  possessing  the  fixtures  necessary  to  the  dis- 


180 


MA^fUFACTURE  OF  COLORS. 


tillation  of  zinc,  the  oxidization  of  its  vapors,  and  the 
collection  of  the  oxide. 

Any  number  of  such  furnaces  could  be  disposed  one 
near  the  other,  each  having  several  retorts.  The  same 
letters  in  these  figures  correspond  with  similar  parts 
in  the  preceding  cuts ;  therefore,  it  is  useless  to  ex- 
plain them  anew.  The  only  difference  is,  that  the 
retorts  may  be  charged  from  the  same  room  in  which 
the  fireplace  is.  The  retort  is  open  at  both  ends  b,  d', 
the  latter  being  that  used  for  charging.  During  the 
distillation,  this  opening  is  kept  hermetically  closed. 

With  this  disposition  it  is  possible  to  dispense  with 
the  chamber  or  cage  h,  and  with  the  floor  k.  Never- 
theless, this  apparatus  is  not  so  advantageous  as 
others,  and  should  be  employed  only  in  case  of  neces- 
sity. 

2d.  Mode  of  Fabrication  by  Murdoch. 

A  method  of  manufacturing  the  oxide  of  zinc, 
several  years  older  than  that  previously  described, 
has  been  indicated  by  Mr.  Murdoch.  Although  there 
is  a  great  analogy  in  the  chemical  processes,  we  shall 
mention  it  here,  in  order  to  complete  the  data  relating 
to  the  oxidization  of  zinc. 

By  the  ordinary  methods  of  preparing  the  oxide  of 
zinc,  air  is  allowed  to  enter  the  retorts  or  vases  hold- 
ing the  metal,  and  oxidizes  the  metallic  vapors.  Part 
of  the  oxide  is  collected  in  pipes  adapted  to  the  retort, 
but  the  greater  portion  remains  in  the  retort  mixed 
with  impurities. 

The  improvement  consists :  1st,  In  i^re venting  the 
access  of  the  air  to  the  molten  zinc  or  to  the 
zinc  furnishing  materials  held  in  the  retort,  and  in 
burning  the  metallic  vapors  on  the  outside  of  that 


WHITE  COLORS. 


181 


vessel  in  which  they  have  been  generated;  2d,  In 
passing  the  mixture  of  air  and  oxide  through  sieves 
or  screens,  which  retain  the  oxide ;  3d,  In  producing 
a  strong  air  blast  or  draft  (by  a  blowing  machine  or 
otherwise)  which  is  passed  through  the  rooms  where 
the  oxide  is  produced  and  collected.  The  operation 
is  thus  assisted  considerably. 

For  the  manufacture  of  zinc  oxide  by  this  process, 
five  rooms  are  employed:  the  retort  room,  the  air 
room,  the  oxidizing  room,  that  for  the  collection,  and 
lastly,  the  inspection  room. 

The  first  of  these  rooms  contains  the  furnace  of  the 
retort  or  generating  vessel ;  and  it  is  there  that  the 
operations  of  charging  and  cleaning  take  place.  The 
retort  which  receives  the  zinc  or  its  ore  is  of  clay, 
and  will  stand  a  white  heat.  It  has  two  openings, 
one  of  which  is  for  charging  and  cleaning,  and  is  kept 
hermetically  closed  during  the  distillation ;  the  other 
is  the  outlet  through  which  the  metallic  vapors 
escape  into  the  oxidizing  room. 

The  air  room  communicates  with  the  outside 
atmosphere,  and  is  provided  with  metallic  or  cloth 
screens  which  allow  of  the  passage  of  the  air,  but 
prevent  that  of  the  floating  dust.  The  air  is  therefore 
in  a  measure  purified. 

One  of  the  extremities  of  the  retort  penetrates  on 
to  one  side  of  the  oxidizing  room,  and,  as  soon  as  the 
metallic  vapors  appear,  they  burn  in  contact  with  the 
air  which  comes  from  the  air  room.  The  white  fumes 
or  flakes  resulting  from  this  combustion  and  which 
are  oxide  of  zinc,  ov  flovjers  of  zinc ^  are  carried  by  the 
draft  into  the  collecting  room.  A  flue  or  trough 
connects  the  latter  room  with  the  stack  of  the  furnace 
and  thus  creates  the  draft.    Several  screens  of  cloth 


182 


MANUFACTURE  OF  COLORS. 


or  metallic  gauze  are  placed  before  the  opening  of  the 
air  trough,  so  as  to  retain  the  oxide  of  zinc.  These 
screens  are  now  and  then,  or  constantly,  shaken,  in 
order  to  separate  the  adhering  oxide  which,  other- 
wise, would  obstruct  the  passage  of  the  air. 

The  inspection  room  is  on  the  opposite  side  of  the 
entrance  of  the  retort  in  the  oxidizing  room.  The 
partition  wall  has  two  openings  :  one  with  a  colored 
glass  to  diminish  the  glare  of  the  burning  metal,  and 
to  allow  of  the  watching  of  the  operation;  the  other 
with  a  small  door  for  passing  and  using  a  scraper, 
should  the  opening  of  the  retort  become  obstructed. 

3d.  Manufacture  of  Zinc  White  at  Portillon,  near  Tours. 

The  owners  of  the  white  lead  works  at  Portillon 
have  also  established,  at  the  same  place,  the  manu- 
facture of  zinc  white  with  a  furnace  holding  seven 
retorts.  The  oxide  of  zinc,  of  which  about  2000  kilo- 
grammes are  produced  every  day,  goes  upwards  after 
its  formation,  and  is  collected  in  a  series  of  cloth 
cylinders,  delivering  it  into  barrels  through  their 
lower  extremities,  which  are  easily  closed  and  opened. 
There  cannot  be  a  loss  of  oxide,  since  the  air  draft 
has  to  pass  through  600  metres  of  collecting  space 
before  it  escapes  into  the  atmosphere.  The  zinc  white 
is  ground  in  oil  by  processes  similar  to  those  em- 
ployed, and  already  described,  for  the  grinding  of 
white  lead  at  the  same  works.  The  oxide  of  zinc  is 
put  wet  into  the  kneading  machine,  but  the  oil  sepa- 
rates the  water  when  the  paste  is  passed  through  the 
grinding  cylinders. 


WHITE  COLOKS. 


183 


4th.  Snovj  White,  Zinc  White,  Hopper  White. 

The  oxide  of  zinc,  obtained  by  the  combustion  of 
the  metallic  vapors  in  atmospheric  air,  is  not  homo- 
geneous. About  one-half  of  the  product  is  exceed- 
ingly light,  and  is  called  snow  white;  the  remainder 
'  is  more  dense,  and  goes  under  the  name  of  zinc  white. 
Painters  affirm  that  the  latter  possesses  greater  body 
or  covering  power  than  the  former.  Therefore,  seve- 
ral manufacturers  have  tried  whether  it  would  not  be 
possible  to  produce  the  dense  quality  without  admix- 
ture of  snow  white.  The  thorough  separation  of  the 
two  oxides  is  not  considered  practicable.  Mr.  Bou- 
quette's  process  consists  in  arranging  and  regulating 
the  drafts  of  air  in  such  a  manner,  near  the  outlets  of 
the  retorts,  that  the  light  snow  white  is  carried 
upwards  into  a  room  above  the  furnace,  whereas  the 
heavy  white  falls  into  a  hopper  underneath  the  dis- 
tilling vessels.    The  operation  is  not  very  regular. 

We  should  remark  that  the  zinc  white  collected  at 
the  beginning  of  the  condensing  apparatus,  near  the 
furnace,  is  a  mixture  of  oxide  of  zinc  with  metallic 
zinc,  and  a  greater  or  less  proportion  of  cadmium, 
iron,  and  copper.  The  oxide  from  the  tail  end  of  the 
condensing  rooms  is  always  lighter,  and  the  two 
kinds  are  generally  mixed  together. 

Mr.  Sorel  thus  describes  a  process  for  separating 
them:  ''A  certain  quantity  of  zinc,  put  into  large 
mufles,  is  heated  only  to  the  point  of  fusion,  and  is 
then  inflamed.  The  burning  will  soon  cease  if  care  be 
not  taken  to  constantly  rake  off*  the  oxide  formed  on 
the  molten  surface.  The  zinc,  which  is  all  the  time 
in  contact  with  the  oxygen  of  the  air,  produces  a  very 
light  oxide,  which  is  carried  away  by  the  draft  into 


184 


MANUFACTURE  OF  COLORS. 


the  collecting  rooms  above  the  furnace.  The  oxide 
remaining  on  the  surface  of  the  bath  is  generally 
contaminated  with  other  metallic  oxides,  and  is 
made  to  fall  into  a  receiver  or  hopper  near  the  fur- 
nace. It  bears  the  name  of  hopper  wJiite,  and  is  not 
so  white  as  that  which  has  been  volatilized.  The 
advantage  of  this  process  is  simply  the  separation  of 
the  two  oxides. 

"Hopper  white  covers  more  than  snow  white, 
but  it  is  not  so  bright.  In  order  to  impart  greater 
density  to  snow  white  it  has  been  suggested  to  cal- 
cine it  in  clay  crucibles,  or,  better  still,  to  make  it 
into  a  paste  with  water,  and  to  form  lumps  which  are 
dried  in  a  stove  room.  The  white,  after  these  opera- 
tions, is  more  diflScult  to  grind,  but  it  covers  more 
and  has  a  better  appearance.'' 

5th.  Saint- Cyr  White. 

Another  product,  manufactured  at  the  works  of 
Portillon,  and  called  Samt-Cyr  white,  is  a  mixture  of 
white  lead  and  zinc  white. 

6th.  Vitry  White. 
This  is  a  mixture  in  variable  proportions  of  zinc 
white  with  sulphate  of  baryta.  It  is  now  seldom 
met  with  in  the  trade  under  that  name,  and,  if  sold 
as  zinc  white,  constitutes  a  fraud  which  should  be 
punished. 

Yth.  Various  Figments  obtained  with  Zinc  White. 

Zinc  white  is  also  employed  as  a  basis  of  various 
pigments  employed  in  j)ainting.  100  parts  in  weight 
of  zinc  white  and — 


WHITE  COLORS. 


185 


1 

part 

of  indigo 

=  azure-white. 

1 

u 

charcoal 

=  pearl-gray. 

100 

u 

gray  zinc  oxide 

=  slate-gray. 

2.5 

u 

chromate  of  zinc  or  lead 

=  straw-yellow. 

6 

u 

yellow  ochre 

=  stone  color. 

3 
3 

u 
u 

yellow  ochre  } 
vermilion  i 

=  chamois. 

10 

u 

sienna  earth 

=  dark  chamois. 

2.5 

u 

chrome  yellow) 

=  lemon. 

2.5 

u 

Prussian  blue  i 

10 

chrome  j^ellow 

=  gold-3'ellow. 

0.9 

u 

Prussian  blue 

=  tint  of  azure-blue. 

0.2 

u 

madder  lake  i 

8 

Prussian  blue 

=  water-green. 

100 

u 

chrome  yellow  | 

=  grass-green. 

8 

u 

Prussian  blue  i 

50 
12 

u 
u 

yellow  ochre  ) 
black  J 

=  olive-green. 

400 

a 

chrome  yellow  \ 

6 

u 

Prussian  blue  >  . 

=  bronze-green. 

6 

u 

black  ) 

For  obtaining  pure  or  mixed  hues,  the  following  v 
substances  are  also  employed:  Ultramarine,  cobalt 
blue,  Prussian  red,  ivory,  bone  and  lamp  blacks, 
oxide  of  manganese,  et.c. 

8th.  Various  Processes  for  the  Manufacture  of  Zinc  White. 

Many  processes  and  apparatuses  have  been  de- 
scribed and  proposed  for  the  manufacture  of  zinc 
white.  They  are  generally  based  upon  the  oxidation 
of  zinc  vapors  by  the  oxygen  of  the  air.  Some 
replace  the  retorts  by  muffles,  or  heat  the  zinc 
directly  upon  the  hearth  of  the  furnace ,  others  em- 
ploy a  pot  of  fire  clay.  Certain  manufacturers 
use  a  draft  of  pure  air ;  others  claim  that  the  gases 
of  the  combustion  of  coke  or  charcoal,  which  have 
been  passed  and  purified  through  lime,  give  a  better 


186 


MANUFACTUllE  OF  COLORS. 


oxidized  zinc  white.  In  countries  where  rich  zinc 
ores  are  found,  zinc  white  is  advantageously  prepared 
by  the  reduction  of  the  ore  with  charcoal. 

The  great  quantities  of  sulphate  of  zinc  produced 
in  galvanic  batteries,  are  now  without  use.  All  its 
component  parts  may  be  utilized  in  the  following 
manner.  By  a  calcination  in  a  clay  vessel,  the 
sulphate  of  zinc,  when  pure,  is  transformed  into  a 
white  and  light  oxide  for  painting,  ai}d  into  sulphu- 
rous acid  which  may  be  dissolved  in  water,  or  used  for 
the  manufacture  of  sulphites,  which  are  now  employed 
in  large  quantities.    Pure  oxygen  is  also  foi'med. 

All  these  processes,  conducted  with  the  proper  care, 
may  furnish  a  zinc  white  of  good  quality.  But  we 
do  not  feel  that  we  should  fill  up  this  manual  with 
more  extended  explanations  of  methods,  which,  after 
all,  do  not  appear  superior  to  those  which  are  well 
known  and  tried. 

We  should  add  that  metallic  zinc  necessarily  in- 
creases in  weight,  by  combining  with  the  oxygen  of 
the  air,  and  that  one  hundred  parts  of  metal  should 
give  about  one  hundred  and  twenty-four  of  oxide. 
But  in  practice,  the  result  is  only  fi'om  one  hundred 
and  ten  to  one  hundred  and  twelve  parts  of  white,  on 
account  of  the  loss  occasioned  by  the  impurities  of 
the  metal,  and  the  waste  of  oxide  carried  away  in  the 
air,  and  escaping  through  cracks  in  the  apparatus. 

9tli.  Uses  of  Zinc  White^  and  Dryers. 

Zinc,  white  mixes  readily  with  all  the  liquids 
employed  for  white  lead,  such  as  oil  and  essence  of 
turpentine;  and  as  it  is  always  in  an  impalpable 
powder,  it  does  not 'need  a  protracted  grinding  to 
acquire  the  ]3i'oper  consistency.  Glue  size  may  also 
be  employed. 


WHITE  COLORS. 


187 


The  advantages  of  zinc  white  are,  that  it  is  scarcely 
poisonous ;  that  it  does  not  change  the  colors  with 
which  it  is  mixed,  and  that  it  does  not  darken  by  the 
fumes  emitted  by  sulphuretted  hydrogen  or  animal 
substances.  On  the  other  hand,  it  is  slow  drying, 
and  dryers  are  necessary. 

We  have  already  seen,  that  in  1845,  Mr.  Leclaire 
had  employed  the  peroxide  of  manganese  for  the 
quick  drying  of  the  zinc  white.  Here  is  the  instruc- 
tion published  by  the  Society  of  the  Yieille-Mon- 
tagne,  in  a  manual  for  the  painters  with  zinc  white  : — 

"  The  peroxide  of  manganese  is  broken  into  pieces 
of  the  size  of  peas,  and  after  sifting  the  smallei-  par- 
ticles, the  remainder  is  thoroughly  dried  upon  a  piece 
of  sheet-iron,  but  without  being  calcined.  It  is  then 
wrapped  in  a  piece  of  strong  cloth,  which  is  after- 
w^ards  placed  in  a  small  basket  of  wire  gauze  with 
very  narrow  meshes. 

"Well  clarified  linseed  oil  is  poured  into  a  kettle, 
which  is  held  upon  an  iron  plate  above  the  fireplace, 
and  the  basket  of  peroxide  of  manganese  is  suspended 
in  it  from  an  iron  rod  crossing  the  kettle. 

"  The  oil  is  brought  to  a  temperature  a  little  below 
the  point  of  ebullition,  and  maintained  there.  Too 
much  heat  will  cause  the  oil  to  boil  over,  and  there  is 
then  great  danger  of  fire.  The  heating  should  last 
twenty-four  hours  for  large  quantities  of  oil. 

"The  operation  is  completed  and  successful,  when 
the  oil  has  acquired  a  reddish  tinge.  It  is  then  left  to 
cool,  is  filtered,  and  packed  in  glass  or  stoneware 
bottles,  which  are  carefully  closed. 

"  The  same  manganese  may  be  used  any  number  of 
times  ;  indeed  it  is  better  when  it  has  already  been 
employed.  Before  using  it  again,  it  is  coarsely  broken 


188 


MA^J^UFACTURE  OF  COLORS. 


in  a  mortar  and  new  manganese  added ;  the  whole  is 
then  sifted,  and  the  proportion  is  fifteen  parts  of  the 
mixture  to  one  hundred  parts  (in  weight)  of  oil. 

"The  first  time  manganese  is  used,  it  is  put  into 
the  oil  only  on  the  second  day  of  the  heating,  because 
fresh  oils  hold  a  little  watei*,  and  the  new  manganese 
might  act  too  powerfully  and  cause  the  inflammation 
of  the  liquid. 

"  If  the  manganese  has  already  been  used,  it  is  put 
into  the  oil  on  the  first  day,  before  lighting  the  fire. 
Less  heating  is  needed  with  fresh  than  with  old  man- 
ganese. In  either  case,  the  fire  is  urged  but  mode- 
rately, and  the  basket  of  manganese  must  be  entirely 
covered  with  oil,  without  touching  the  sides  of  the 
kettle. 

"  If  the  dryer  be  too  thick  from  a  strong  heating, 
essence  of  turpentine  may  be  added  to  it  when  it  is 
nearly  cold,  otherwise  there  is  danger  of  inflammation. 
The  proportion  of  the  essence  should  be  sufiicient 
to  reduce  the  dryer  to  the  proj^er  consistency  for 
using  and  keeping  it." 

In  his  Cliimie  des  Cotdeurs,  Mr.  J.  Lefort  makes  the 
following  observations  on  dryers  : — 

"  In  order  to  render  dryers  suitable  for  every  kind 
of  painting,  and  to  facilitate  their  transportation,  it 
has  been  proposed  to  mix  them  with  slaked  caustic 
lime.  But  as  the  latter  contains  an  excess  of  water, 
it  is  heated  at  a  moderate  temperature  in  a  draft  of 
hot  air,  until  the  powder  feels  dry.  The  combination 
is  a  real  drying  calcareous  soap,  which  being  ground 
with  colors  and  ordinary  linseed  oil,  is  a  good  sub- 
stitute for  drying  oil.  From  four  to  six  parts  of  dry- 
ing soap  in  powder,  are  sufficient  for  one  hundred 
parts  of  oil. 


WHITE  COLORS. 


189 


"  Peroxide  of  manganese,  especially  when  powdered, 
communicates  to  the  oil  a  reddish  tinge  which  is  dis- 
agreeable for  fine  white  painting.  Of  late  years, 
this  inconvenience  has  been  remedied  by  the  use  of 
white  salts  of  manganese  ;  and  experience  proves  that 
the  majority  of  soluble  salts  of  protoxide  of  mangan- 
ese and  zinc  (sulphates,  chlorides,  acetates),  when 
ground  with  ordinary  linseed  oil  and  zinc  white,  im- 
part to  the  latter  the  drying  property  it  was  deficient 
in. 

"  It  is  absolutely  necessary  that  these  various  salts 
should  be  entirely  deprived  of  their  combined  water. 
Therefore,  they  are  thoroughly  dried  upon  plates 
heated  at  from  80°  to  100°  C,  until  they  are  perfectly 
white  and  opaque.  They  are  then  mixed  in  equal 
proportions,  and  finely  powdered. 

"These  dryers  which  have  been  patented,  and  which 
are  constantly  employed  in  painting  with  zinc,  are 
composed  of  sulphate  of  zinc  and  acetate  of  mangan- 
ese, or  of  sulphate  of  manganese  and  acetate  of  zinc. 
Three  or  four  parts  are  suflftcient  with  the  proper 
quantity  of  ordinary  linseed  oil,  for  one  hundred  parts 
of  zinc  white." 

Moreover,  we  shall  examine  anew,  in  a  subsequent 
chapter,  the  various  dryers  and  compositions  which 
have  been  proposed. 

loth.  Adulteration  of  Zinc  White. 

Zinc  white  is  adulterated  with  sulphate  of  baryta 
and  sulphate  of  lime. 

The  first  adulteration  is  recognized  by  dissolving 
the  oxide  of  zinc  in  diluted  nitric  acid,  when  the  sul- 
phate of  baryta  remains  as  an  insoluble  residuum. 

The  separation  of  the  sulphate  of  lime  is  more 


190 


MANUFACTURE  OF  COLORS. 


difficult.  The  adulteration  is  generally  made  with  a 
perfectly  white  sulphate  of  lime,  in  impalpable  powder, 
which  is  sometimes  called  atomic  sulj^hate.  The  sus- 
pected sample  of  zinc  white  is  dissolved,  with  the  aid 
of  heat,  in  a  small  quantity  of  concentrated  nitric 
acid.  The  solution  is  diluted  with  five  or  six  times 
its  weight  of  distilled  water,  then  saturated  with 
ammonia,  and  a  few  drops  of  oxalate  of  ammonia 
poured  in.  The  precipitate  of  oxalate  of  lime  is  col- 
lected upon  a  filter,  calcined,  and  transformed  into 
carbonate  which  is  weighed.  A  solution  of  chloride 
of  barium,  poured  into  the  filtered  liquor,  produces  a 
sulphate  of  baryta  which  is  insoluble  in  water  and  in 
concentrated  acids. 

If  the  sample  be  already  ground  in  oil,  10  grammes 
of  it  are  calcined  in  a  porcelain  crucible,  and  when  all 
the  oil  is  decomposed,  the  cold  residuum  is  treated 
by  distilled  water.  A  few  drops  of  nitric  or  sulphuric 
acid  poured  into  the  liquor,  will  disengage  sulphu- 
retted hydrogen  in  greater  proportion  as  the  sample 
is  more  adulterated. 

If  the  oil  has  been  rendered  drying  by  compositions 
of  lime  and  sulphate  of  zinc,  these  substances  should 
be  determined  by  analysis,  and  taken  into  account  in 
the  search  for  the  adulteration  of  the  sample. 

11th.  Danger  and  Salubrity  of  Zinc  White. 

When  this  pigment  began  to  be  largely  used  in 
painting,  its  salubrity  was  considerably  discussed. 
Some  persons  pretended  that  it  was  as  dangerous  as 
white  lead;  others,  on  the  contrary,  that  it  was 
entirely  innocuous.  Facts  were  brought  forward  by 
each  party;  but,  without  burdening  this  volume  with 
all  the  documents  on  the  question,  it  is  certain  that 


WHITE  COLOKS. 


191 


zinc  white  is  not  so  dangerous  as  white  lead  to  the 
health  of  either  the  workmen  or  that  of  the  consumei's. 
^Nevertheless,  it  is  not  entirely  innocuous,  and,  in 
certain  cases,  it  has  produced  slight  sickness,  which 
may  be  avoided  by  cai'e  in  its  manipulation. 

12th.  Use  of  Blende  as  a  Substitute  for  White  Lead  and  Zinc  White. 

Blende,  or  sulphide  of  zinc,  in  the  opinion  of  Mr. 
de  Certeau,  may  be  advantageously  and  cheaply  sub- 
stituted for  white  lead  or  zinc  white  in  all  the  colors 
for  painting.  Its  impalpable  powder  ground  in  dry- 
ing oils,  with  or  without  essence  of  turpentine,  will 
cover  at  least  as  well  as  white  lead  and  zinc  white, 
and  the  coats  flow  more  easily  under  the  brush.  This 
color  is  very  fast  and  durable,  and  does  not  change 
the  other  pigments  with  which  it  is  mixed. 

The  only  disadvantage  of  blende  is  that  it  is  always 
more  or  less  colored.  The  inconvenience  is  slight 
with  those  blendes  which  are  colored  a  honey -yellow, 
and  which  are  rightly  considered  the  purest.  That 
variety,  when  finely  comminuted,  gives  a  grayish- 
white  powder  with  a  yellow  tinge,  which  may  be 
employed  for  light  colors  in  house  painting.  Mixed 
with  1  per  cent,  of  artificial  ultramarine,  it  produces 
a  gray  coat,  slightly  greenish.  If,  instead  of  blue,  a 
small  proportion  of  vermilion  or  ochre  be  added,  the 
color  is  pinkish.  With  chrome  yellow  and  a  little 
red,  we  obtain  a  chamois.  A  pearl-gray  is  obtained 
by  increasing  the  whiteness  of  the  blende  with  ten  or 
twenty  per  cent,  of  zinc  white,  and  adding  1  per  cent, 
of  black. 

Brown  or  reddish  blendes  cannot  be  employed  in 
the  preparation  of  light  colors,  such  as  those  we  have 
just  mentioned;  but  they  may  be  successfully  used 


192 


MANUFACTURE  OF  COLORS. 


for  dark  colors,  such  as  brown,  black,  maroon,  olive- 
green,  mahogany,  etc. 

There  is  no  advantage  in  using  roasted  blendes, 
instead  of  the  natural  ones ;  because,  by  roasting, 
blende  loses  about  one-sixth  of  its  weight,  generally 
becomes  darker,  and  covers  less.  However,  as  roast- 
ing changes  the  color  of  the  substance  sensibly,  it  is 
an  easy  process  of  obtaining  certain  tones  and  hues, 
which  could  not  be  produced  so  cheaply  in  another 
way.  Therefore,  roasted  blende  may,  by  its  mixture 
with  the  natural  one,  add  new  tones  and  hues  to  the 
colors  resulting  from  this  material. 

Powdered  blende  is  far  from  being  as  dangerous  as 
white  lead.  Therefore,  in  the  opinion  of  Mr.  de 
Certeau,  that  substance  possesses  the  advantage  of 
popularizing  the  use  of  oil  paints  as  well  by  a  great 
reduction  in  prices,  as  by  diminishing  the  use  of  a 
dangerous  substance  (white  lead). 

§  10.  Baryta  whites. 

1st.  Natural  Sulphate  of  Baryta. 

The  sulphate  of  Baryta,  or  Barytes,  heavy  spar, 
Barytine,  Baroselenite,  hepatite,  stinking  stone,  Bo- 
logna stone,  etc.,  is  a  white  or  reddish  substance,  very 
dense,  which  is  found  in  the  natural  state  forming 
veins  with  the  ores  of  lead,  silver,  mercury,  etc.,  and 
in  many  other  rocks.  It  contains  34.37  parts  of 
sulphuric  acid  and  65.63  parts  of  baryta. 

Heavy  spar  is  employed  in  the  manufacture  of  a 
handsome  white  color,  entirely  innocuous,  fast  and 
resisting  most  reagents,  but  with  little  body  or  cover- 
ing power.  This  white,  fixed  with  glue  size,  is 
largely  employed  in  the  manufacture  of  paper  hang- 
ings.   It  is  also  used  for  adulterating  white  lead  and 


WHITE  COLORS. 


193 


zinc  white.  We  have  previously  said,  that,  in  Ger- 
many, it  was  customary  to  add  to  it  white  lead  for  the 
preparation  of  Venice  and  Hamburg  whites.  In 
Austria,  the  pure  sulphate  of  baryta  is  still  sold  under 
the  incorrect  name  of  Tyrolese  white  lead. 

In  preparing  the  sulphate  of  baryta  for  the  arts, 
the  whitest  lumps  of  native  ore  are  picked  out,  and 
coarsely  broken,  and  charged  into  reverberatory  fur- 
naces. The  heat  applied  is  solely  intended  for  dis- 
integrating the  substance,  and  arriving  at  a  finer 
degree  of  pulverization.  The  grinding  is  done 
dry,  and  the  fine  resulting  powder  is  thrown  into 
large  tanks  filled  with  water.  By  stirring,  and  then 
letting  it  stand  a  little  while,  the  heavier  and  coarser 
particles  fall  to  the  bottom.  The  water  above, 
which  has  the  appearance  of  milk,  is  decanted  into 
settling  basins,  where  the  lighter  suspended  material 
has  time  to  deposit.  After  another  decantation  of  the 
clear  liquor,  the  pasty  white  is  collected,  and  dried  in 
the  air  or  in  a  stove  room.  It  is  then  a  very  bright 
and  dense  white. 

2d.  Artificial  Sulphate  of  Baryta^  Blanc  Fixe. 

For  several  years  we  have  found  in  the  market, 
under  the  name  of  hlanc  fixe  (fast  white),  an  arti- 
ficial sulphate  of  baryta,  which  is  much  better  than 
the  native  sulphate.  We  owe  it  principally  to  Mr.  F. 
Kuhlmann,  of  Lille,  one  of  the  greatest  manufacturing 
chemists  of  France.  Mr.  Kuhlmann,  in  a  memoir, 
read  before  the  Academy  of  Sciences,  has  described 
the  mode  of  preparation  and  the  properties  of  this 
product,  and  we  cannot  do  better  than  to  present  an 
extract  from  that  memoir,  which  we  do  as  follows: — 

"  In  order  to  produce  the  artificial  sulphate  of 
13 


194 


MA^q^TJFACTUKE  OF  COLORS. 


baryta  at  a  moderate  price,  I  have  endeavored  first  to 
reduce  the  cost  of  the  acids  which  constitute  the 
main  expense  of  its  manufacture.  I  have,  therefore, 
tried  more  completely  to  condense  the  acid  vapors, 
part  of  which  are  lost  in  our  soda  works  to  the  preju- 
dice of  the  manufacturers,  of  the  public  health,  and 
of  vegetation. 

"By  putting  the  natural  carbonate  of  baryta  (withe- 
rite),  large  deposits  of  which  are  to  be  found  in  the 
north  of  England,  in  contact  with  the  vapors  escaping 
from  the  salt  decomposing  furnaces  or  from  the  lead 
chambers,  I  have  succeeded  in  saving  a  large  propor- 
tion of  the  uncondensed  vapors  which  no  longer  in- 
commode the  neighborhood  or  injure  vegetation. 

"In  my  works  the  baryta,  dissolved  by  the  con- 
densed acids,  is  converted  into  the  artificial  sulphate 
by  an  addition  of  sulphuric  acid.  The  recovered 
nitric  and  hydrochloric  acids  return  to  take  part  in  a 
new  operation,  and  increase  the  yield.  I  thus  realize 
the  double  advantage  to  which  my  experiments  have 
tended. 

"But  there  is  a  loss  of  hydrochloric  acid  much 
greater  than  that  resulting  from  imperfect  condensing 
apparatus,  i.  e.,  that  resulting  from  the  manufacture 
of  chlorine  or  bleaching  powder,  which  consumes  the 
greater  proportion  of  the  acid. 

"There  is  no  chemist  who  has  not  deplored  the 
fact,  that  more  than  one-half  of  the  hydrochloric  acid 
used,  is  lost  in  the  state  of  chloride  of  manganese. 
This  loss,  in  practice,  amounts  to  two-thirds,  on 
account  of  the  impurities  in  the  oxide  of  manganese. 
Its  magnitude  may  be  made  apparent  in  considering 
that  the  manufacture  of  artificial  soda,  in  France, 
consumes  per  year  oyer  sixty  millions  of  kilogrammes 


WHITE  COLORS. 


195 


of  common  salt.  I  think  that  I  am  below  the  reality 
in  saying  that  the  indicated  loss  amounts  to  two 
millions  of  francs  per  year,  in  France  alone. 

"  That  great  loss  has  caused  many  to  make  search 
as  to  whether  the  residue  of  the  manufacture  of  chlo- 
rine could  not  be  made  available  and  valuable.  Not- 
withstanding many  trials,  the  new  uses  have  been 
few,  and  absorbing  but  a  small  proportion  of  the 
waste  materials.  This  chloride  of  manganese  has 
been  applied  to  the  purification  of  gas  light,  to  the 
production  of  ammoniacal  salts,  and  to  disinfecting 
cesspools.  In  the  large  works  of  Mr.  Tennant,  near 
Glasgow,  experiments  have  been  made  to  regenerate 
the  oxide  of  manganese,  so  as  to  use  it  again  in  the 
manufacture  of  chlorine.  All  their  uses  amount  to 
little  as  regards  the  enormous  quantity  of  residue. 
In  the  majority  of  cases,  the  price  at  which  the  chlo- 
ride of  manganese  is  sold  is  scarcely  sufficient  to 
cover  the  expense  of  concentration  or  calcination. 

"  Therefore,  the  liquid  residue  of  the  manufacture 
of  chlorine  has  generally  remained  a  cause  of  embar- 
rassment to  chemical  works,  and  even  of  danger  to 
general  salubrity,  whether  it  was  let  into  running 
waters  or  lost  in  the  ground  through  absorbing  wells. 

"After  having  condensed  the  acids  lost  in  the  air, 
all  my  eftbrts  have  tended  to  the  saving  of  those 
held  in  the  liquid  residue. 

"I  have  had  the  satisfaction  of  succeeding  com- 
pletely by  using  a  reaction  analogous  to  that  by 
which  Leblanc  gave  to  France  the  manufacture  of 
artificial  soda. 

"In  the  Leblanc  process,  a  mixture  in  proper 
proportions  of  sulphate  of  soda,  chalk,  and  coal,  is 


/ 


196 


MANUFACTURE  OF  COLORS. 


transformed,  at  a  high  temperature,  into  insoluble 
oxysulphide  of  calcium  and  soluble  carbonate  of  soda. 

"In  my  process,  a  mixture  in  proper  proportions 
of  natural  sulphate  of  baryta,  chloride  of  manganese, 
and  coal,  is  transformed  under  the  influence  of  a  high 
temperature,  into  insoluble  sulphide  of  manganese, 
and  chloride  of  barium,  which  is  easily  separated  by 
washing.  The  reaction  may  be  represented  by  the 
formula — 

BaO,S03  +  MnCl  +  4C  =  BaCl  +  MnS  +  4C0. 

"A  similar  reaction  applies  equally  well  to  the 
chloride  of  iron,  which  constantly  accompanies  the 
chloride  of  manganese. 

"The  coal  intervenes  always  as  a  deoxidizing 
agent,  and  is  converted  into  carbonic  oxide. 

"After  several  preliminary  trials,  rendered  neces- 
sary by  the  impurities  of  the  materials  employed,  the 
correct  proportions  were  determined  upon.  The  re- 
sults are  beyond  my  expectations,  inasmuch  as  I  am 
now  able  to  transform  native  sulphate  of  baryta  into 
chloride  of  barium  without  a  loss  of  more  than  3  to  4 
per  cent,  of  sulphate  of  baryta  lost  or  undecomposed. 

"  Here  is  the  practical  mode  of  working :  The 
transformation  is  effected  in  large  reverberatory  fur- 
naces, similar  to  those  employed  for  decomposing 
common  salt  in  soda  works,  with  a  hearth  divided 
into  two  compartments  by  a  low  wall.  When  these 
furnaces  have  been  heated  for  a  certain  length  of  time, 
the  portion  most  remote  from  the  fireplace  is  charged 
with  a  finely-pulverized  mixture  of  native  sulphate  of 
baryta  and  bituminous  coal-;  and  above  it  there  is 
poured  the  liquid  residue  from  the  manufacture  of 
chloride,  the  free  acid  of  which  has  been  previously 


WHITE  COLOK8. 


197 


saturated  with  chalk  or,  better  still,  with  native  car- 
bonate of  baryta.  The  mixture  is  well  stirred,  and  is 
thickened  by  the  heat.  When  it  has  become  a  thick 
paste  it  is  passed  over  the  partition  wall,  with  proper 
iron  tools,  into  the  compartment  near  the  fire.  There 
the  mass  becomes  swollen  and  soon  disengages  small 
gas  jets  of  carbonic  oxide,  similar  to  those  produced 
at  a  certain  period  of  the  soda  manufacture,  but,  in 
this  case,  having  a  green  tinge  due  to  the  baryta. 
After  an  hour  of  calcination  at  a  red  heat,  the  semi- 
fluid paste,  which  has  a  little  more  consistency  than 
that  of  crude  soda,  is  removed  from  the  furnace,  and, 
when  cold,  forms  a  black  mass  of  chloride  of  barium, 
with  the  sulphides  of  manganese  and  iron,  and  a 
small  proportion  of  hyposulphite  of  baryta.  After 
several  days  of  exposure  to  the  air,  the  mass  becomes 
disintegrated,  and  the  hyposulphite  passes  to  the 
state  of  sulphate  of  baryta.  The  substances  are  then 
lixiviated  with  hot  water  in  an  apparatus  disposed 
like  that  for  crude  soda. 

"  The  liquors  are  a  clear  solution  of  nearly  pure 
chloride  of  barium.  Should  there  be  a  slight  excess 
of  sulphide  of  barium,  causing  a  yellow  coloration, 
there  is  poured  in,  until  complete  decoloration,  a 
solution  of  chloride  of  manganese  (residue  of  the 
manufacture  of  chlorine)  which  has  been  deprived  of 
iron  by  digestion  with  powdered  carbonate  of  baryta. 
Conversely,  any  excess  of  chloride  of  manganese  is 
separated  with  sulphide  of  barium.  Thus,  we  see 
that  there  is  no  practical  difficulty  in  obtaining  a  very 
pure  chloride  of  barium. 

"Such  is  the  method  followed  in  my  works  for 
utilizing  the  residue  of  the  manufacture  of  chlorine. 


198 


MANUFACTURE  OF  COLORS. 


As  it  is  of  great  importance,  I  shall  give  a  few  more 
details. 

"  The  solution  of  chloride  of  barium,  obtained  from 
the  raw  product,  marks  24  or  25°  Be.  When  it  has 
been  purified  in  the  manner  indicated  above,  chamber 
acid  (sulphuric),  diluted  with  water  to  mark  30°  Be., 
is  poured  into  it  as  long  as  a  precipitate  is  formed. 
The  whole  is  then  well  stirred  and  let  to  stand.  The 
sulphate  of  baryta  is  rapidly  deposited,  and  the 
syphoned  liquors  constitute  a  hydrochloric  acid 
marking  6°  Be. 

"  The  artificial  sulphate  thus  obtained  is  washed 
in  a  methodical  way,  in  order  to  remove  the  last  trace 
of  free  acid.  It  is  then  drained  to  the  consistency  of 
a  firm  paste  in  cloth  filters,  and  the  operation  will  be 
more  rapid  if  the  filters  are  pressed,  or  subjected  to 
centrifugal  action.  When  the  paste  has  become  thick 
enough,  it  is  packed  in  barrels,  and  contains  from  30 
to  32  per  cent,  of  water. 

"It  may  be  dried  and  moulded  into  lumps,  like 
white  lead.  However,  in  the  majority  of  cases,  it  is 
more  advantageous  to  use  it  in  the  pasty  state, 
because,  once  dried,  it  does  not  reacquire  the  same 
degree  of  comminution  it  possessed  at  the  time  of  its 
precipitation. 

"  If  I  insist  upon  this  method  of  utilizing  the  waste 
of  the  manufacture  of  chlorine,  it  is  because  it  appears 
to  me  as  presenting  many  economical  results.  Thus, 
in  the  preparation  of  satin  paper  hangings  and  of 
glazed  pasteboard,  the  artificial  sulphate  of  baryta, 
under  the  name  of  hlancfixe,  has  found  its  place.  Its 
consumption  extends  considerably  for  distemper  and 
silicious  painting,  and  for  calsomining  ceilings.  The 


BLUE  COLORS. 


199 


actual  production  of  my  works  amounts  to  2000 
kilogrammes  per  day. 

"  This  substance  possesses  an  unexpected  property, 
upon  which  I  shall  insist :  it  seems  to  form  a  slow, 
but  intimate,  combination  with  the  soluble  alkaline 
silicates,  and  with  these  salts  forms  pigments  of 
unmatched  whiteness,  possessing  a  certain  lustre,  and 
entirely  unacted  upon  by  sulphuretted  hydrogen.  It 
may  also  be  employed  for  fixing  other  colors.  A 
paint  made  of  a  mixture  of  zinc  white  and  blanc  fixe, 
acquires  such  an  adherence  and  durability,  that  it  may 
be  safely  applied  upon  old  oil  painting.  Such  a 
result  is  of  the  greatest  importance  for  Paris,  London, 
Brussels,  and  other  large  cities,  where  carefully  built 
dwellings  are  covered  with  expensive  oil  paintings, 
which  require  to  be  often  renovated." 

SECTION  IL 

BLUE  COLORS. 

The  same  substances  which  furnish  blue  present  a 
very  great  many  tones  of  that  color.  It  will  also  be 
remarked  that  the  purest  and  brightest  blues  are,  at 
the  same  time,  the  most  durable. 

The  hlues  most  frequently  used  in  painting  are: 
Ultramarine,  Cobalt  hlue,  Prussian  blue,  mineral  blue, 
Indigo,  various  kinds  of  azure,  etc. 

§  1.  Prussian  blue. 

This  color  was  discovered  in  1720  by  Diesbach,  of 
Berlin,  and  then  studied  out,  theoretically  and  prac- 
tically, by  many  chemists  and  manufacturers. 

Prussian  blue  is  now  considered  by  all  chemists  to 


200 


MANUFACTURE  OF  COLORS. 


be  a  combination  of  cyanogen  with  iron  in  two  states 
of  oxidation;  that  is  to  say,  a  combination  in  vari- 
able proportions  of  protocyanide  and  sesquicyanide 
of  iron  with  a  little  water. 

As  the  composition  of  Prussian  blue  is  not  con- 
stant, and  may  vary  with  the  proportions  of  the 
two  cyanides  of  iron,  this  pigment  is  found  in  the 
trade,  j)ossessing  a  variable  intensity  of  coloration. 
This  diversity  is  due  not  only  to  the  variable  propor- 
tions of  the  cyanides,  but  also  to  the  mode  of  prepa- 
ration, the  quality  of  the  raw  materials,  and  to  the 
care  in  the  manufacture.  The  average  composition 
of  Prussian  blue  is :  three  equivalents  of  protocyanide 
of  iron,  two  of  sesquicyanide,  and  nine  equivalents  of 
water. 

When  pure,  and  recently  precipitated,  it  is  in  the 
.shape  of  blue  flakes,  which  are  so  deeply  colored  that 
they  appear  black.  After  drying,  the  lumps  are  blue- 
black,  with  a  reddish  reflex. 

The  pure  article  of  the  laboratories  is  made  by 
pouring  a  solution  of  yellow  prussiate  of  potash 
(ferrocyanide  of  potassium),  into  a  salt  of  sesquioxide 
of  iron.  This  process  is  too  long  and  expensive  to  be 
used  in  the  arts,  and  other  methods  are  employed,  one 
of  which  begins  with  the  preparation  of  the  cyanide 
of  potassium,  by  the  calcination  of  carbonate  of  potassa 
with  animal  substances. 

1st.  Manufacture  of  Ordinary  Prussian  Blue. 

A.  ^trst  process, — The  animal  substances  ordinarily 
employed  in  the  manufacture  are :  dried  blood,  hair, 
wool,  waste  from  skins  and  leather,  flesh,  animal  oils, 
soot,  and  bone  black,  etc. 

Dried  blood  is  preferred  for  the  preparation  of  the 


BLUE  COLORS. 


201 


cyanide.  The  fresh  blood  is.  rapidly  evaporated  in 
cast  or  sheet-iron  pans,  and  the  mass  is  constantly 
stirred  "with  an  iron  tool,  until  it  is  entirely  clotted. 
The  drying  is  then  finished  in  the  sun,  and  the 
powdered  material  is  kept  for  use  in  open  vessels. 

10  parts  of  the  powdered  blood  are  moistened  with 
1  part  of  pure  carbonate  of  potassa  dissolved  in  water, 
and  1  per  cent,  of  iron  filings  are  added  to  the  mix- 
ture, which  is  heated  in  a  cast-iron  pan  for  seven  or 
eight  hours,  and  at  a  red  heat.  During  the  first  hours 
of  the  calcination,  abundant  fumes  are  disengaged, 
which  possess  a  very  disagreeable  smell,  and  are 
afterwards  replaced  by  bright  and  reddish-white  jets 
of  flame.  The  mixture  is  stirred,  and,  when  it  is  in 
the  state  of  quiet  fusion  and  does  not  emit  jets  of 
burning  gases,  the  cover  is  put  upon  the  kettle,  and 
the  heat  continued  for  two  hours  more.  The  cakes  of 
the  cooled  product  are  lixiviated  with  hot  water  until 
all  the  soluble  matters  are  removed. 

The  resulting  hlood  lye,  as  it  is  sometimes  called, 
is  a  light  yellow,  and  smells  of  prussic  acid  strongly. 
It  is  not  a  solution  of  pure  cyanide  of  potassium,  but 
contains,  besides,  a  certain  amount  of  carbonate  of 
potassa,  of  sulphates  and  phosphates  of  potassa  and 
lime,  of  sulphide  of  potassium,  etc. 

This  concentrated  and  filtered  lye  is  poured  by 
degrees  into  a  hot  solution  of  one-half  part  of  pure 
sulphate  of  iron,  and  a  variable  proportion  of  alum, 
depending  on  the  quality  of  the  blue  desired.  The 
quality  more  generally  called  Prussian  blue  is  ob- 
tained with  one  part  of  alum  to  seven  or  eight  parts 
of  sulphate  of  iron.  The  ordinary  blue  employs  one 
part  of  alum  to  two  or  three  parts  of  sulphate  of  iron; 


202 


MANUFACTURE  OF  COLORS. 


and  the  inferior  qualities  are  made  with  equal  parts 
of  sulphate  of  iron  and  alum. 

At  each  addition  of  the  cyanide  lye  to  the  iron 
solution,  there  is  an  abundant  production  of  hydro- 
sulphuric  and  carbonic  acids,  and  the  escape  of  these 
gases  is  aided  by  stirring  the  liquor  with  a  wooden 
rod.  The  precipitate  is  brownish-green,  and  is 
washed  with  pure  water,  until  it  turns  entirely  blue. 

After  settling,  and  decanting  the  liquors,  the  blue 
precipitate  is  placed  upon  a  cloth  filter,  where  it  is 
washed  with  water  holding  a  small  proportion  of 
sulphuric  acid.  The  drained  blue  is  then  pressed  in 
boxes,  in  order  to  remove  the  greater  part  of  its  water, 
and  the  thick  resulting  paste  is  divided  into  rectan- 
gular blocks,  which  are  dried  in  the  dark,  or  in  a 
stove-room,  the  temperature  of  which  should  not  be 
above  25°  to  30°  C. 

Prussian  blue,  in  the  opinion  of  Mr.  Bourgeois,  is 
the  next  in  purity  of  tones  after  ultramarine  and  co- 
balt blues ;  and,  although  it  is  inferior  to  these  in 
durability,  it  contains  much  more  coloring  power — 
from  ten  to  eleven  times,  with  equal  volumes.  It  is 
to  be  regretted  that  all  the  alkalies  alter  Prussian 
blue,  so  that,  if  it  be  combined  with  other  alkaline 
pigments,  it  may  rapidly  change  or  disappear.  Mr. 
Bourgeois  indicates  a  process  for  ascertaining  the 
presence  of  Prussian  blue  in  suspected  samples  of 
lazulite  and  cobalt  blues,  which  is  based  upon  the 
discoloration  of  Prussian  blue  by  alkalies.  A  pinch 
of  ultramarine  or  cobalt  blue,  is  digested  for  about 
one  hour  in  a  small  quantity  of  lime-water.  The 
presence  of  Prussian  blue  will  be  detected  by  the  lime- 
water  turning  lemon  yellow,  and  by  an  ochreous  pre- 
cipitate. 


BLUE  COLORS. 


203 


Large  quantites  of  Prussian  blue  are  used  by  house 
painters  and  decorators,  and  by  manufacturers  of 
paper  hangings. 

Of  all  blues,  Prussian  blue  is  the  most  intense. 
Mixed  with  white  lead,  the  hue  is  slightly  greenish. 
A  mixture  of  one  gramme  of  Prussian  blue  and  ninety 
grammes  of  white,  produces  a  sky  blue ;  two  hundred 
grammes  of  white,  and  one  of  blue,  give  an  azure  white. 
In  order  to  judge  well  of  the  beauty  of  a  Prussian 
blue,  it  should  be  incorporated  with  from  fifty  to  one 
hundred  times  its  weight  of  fine  white  lead.  Mixed 
with  from  fifteen  to  twenty  times  its  weight  of  chrome 
yellow,  it  produces  handsome  greens,  not  very  lasting 
however.  Prussian  blue  is  employed  either  with  glue 
size  or  oil ;  but,  in  the  latter  case,  it  should  not  be 
kept  too  long  without  being  applied,  because  it  be- 
comes thick  and  does  not  flow  well  under  the  brush. 
The  pure  blue  ground  in  oil  produces  velvety  blacks 
which  could  not  be  arrived  at  by  the  employment  of 
black  pigments.  We  should  remark  that  old  damp 
walls  destroy  the  color  of  Prussian  blue,  by  the  nitrate 
of  lime  they  contain.  There  is  produced  by  double 
decomposition,  a  ferrocyanide  of  calcium,  and  a  nitrate 
of  iron. 

B.  Second  process. — "W  e  have  seen  that  in  the  first 
process,  a  lye  of  impure  cyanide  of  potassium  was 
prepared.  As  this  operation  is  unwholesome,  on 
account  of  the  deleterious  gases  produced,  other 
modes  of  manufacture  have  been  adopted,  which 
allow  of  the  manufacture  of  Prussian  blue  in  in- 
habited places.  The  ferrocyanide  of  potassium  (yel- 
low prussiate  of  potash)  is  employed,  and  may  be 
prepared  in  a  special  locality,  in  the  following  man- 


204 


MANUFACTURE  OF  COLORS. 


This  second  process  has  nearly  everywhere  taken 
the  place  of  the  first.  The  mixture  consists  of  seventy- 
five  parts  (kilogrammes  for  instance)  of  good  car- 
bonate of  potassa,  fifty  parts  of  horn  or  leather  waste, 
and  three  of  iron  filings.  The  potash  is  introduced 
first  into  a  furnace  which  we  shall  describe  further  on. 
When  it  has  arrived  at  the  point  of  igneous  fusion, 
the  iron  filings  are  introduced  and  mixed  in  the  mass 
with  an  iron  tool,  which  has  been  heated  red  before- 
hand, otherwise  the  stuff  attaches  to  it  and  renders  the 
operation  diflScult. 

When  the  mass  is  thoroughly  in  fusion,  a  shovelful 
of  horn  waste  or  animal  charcoal  is  thrown  into  it 
every  ten  minutes.  At  the  last  addition  of  animal 
matter,  a  strong  heat  is  maintained  for  about  one  and 
a  half  hours,  and  the  operation  is  completed  when  jets 
of  carbonic  oxide  burn  on  the  surface  of  the  bath. 
The  substances  are  then  removed  with  red-hot  iron 
ladles,  and  deposited  in  iron  kettles,  where  they  are 
afterwards  boiled  with  water.  After  two  boilings, 
settlings,  and  decantations,  the  residue  is  removed 
and  again  thoroughly  washed  in  cloth  sacks.  All 
the  liquors  are  evaporated  to  the  proper  degree,  and, 
by  cooling,  give  crystals  of  ferrocyanide  of  potassium, 
which  are  rendered  purer  by  another  solution  and 
crystallization. 

With  the  proportions  indicated  above,  the  product 
is  from  seventeen  to  twenty  parts  of  ferrocyanide. 

The  mother  liquors  are  evaporated  to  dryness,  and 
their  potassa  is  used  for  another  operation.  The 
charred  residue  is  of  no  value. 

The  calcination  of  the  substances  is  effected  in  a 
reverberatory  furnace  having  the  following  dimen- 
sions :  height  of  arch  0.50  metre,  over  the  horizontal 


BLUE  COLORS. 


205 


bed  or  hearth,  which  is  1  square  metre.  The  fireplace 
is  sideways,  0"^.21  X  0™.48,  and  bridge  wall  is  0"".27 
or  0.5  metre  wide.  On  top  of  the  arch,  there  is  an 
opening  covered  with  a  sheet-iron  hood  and  chimney. 
The  wide  working  front  of  the  furnace  is  closed  by 
two  cast-iron  doors,  having  on  their  line  of  junction 
a  hole  large  enough  to  introduce  and  operate  the 
stirring  hooks. 

The  animal  charcoal  is  prepared  either  in  cylinders 
or  in  cast-iron  pots,  or  in  muffles  of  the  same  metal. 
We  shall  also  indicate  a  few  of  the  more  recent  pro- 
cesses which  have  been  proposed  for  the  manufacture 
of  ferrocyanide  of  potassium  or  of  Prussian  blue. 

2d.  Brunnquell  Process, 

Mr.  E.  Brunnquell,  who  has  managed  for  a  long 
time  a  manufactory  of  ferrocyanide  of  potassium, 
near  Bremen,  has  published  in  Berlin  a  long  memoir 
on  this  subject.  We  cannot  reproduce  it  entirely,  but 
we  shall  give  some  extracts  taken  from  the  Technolo- 
giste,  vol.  18,  pages  243  and  291. 

Let  us  state  first  that  the  author  has  examined 
several  processes  for  the  manufacture  of  ferrocyanide 
of  potassium,  and  particularly,  the  one  in  which  the 
ammonia  produced  during  the  carbonization  is 
brought  in  contact  with  potassa  and  charcoal,  at  a 
high  temperature.  He  observes  that,  however  advan- 
tageous these  processes  may  appear,  they  are  not  well 
adapted  for  manufacturing  operations. 

Considering  the  defects  of  the  actual  process,  there 
remains  for  the  manufacturer  to  diminish  the  loss  by 
a  careful  attention  to  certain  details  of  the  operation. 
There  are  two  ways  of  arriving  at  this  result :  First, 
to  aid,  as  far  as  practicable,  the  secondary  formation 


206  MANUFACTURE  OF  COLORS. 


of  cyanogen  (by  ammonia  and  incandescent  charcoal); 
second,  to  avoid  the  loss  of  potassa  by  using  pure 
animal  substances,  and  by  preventing  the  contact  of 
the  ashes  of  the  fireplace.  .  The  author,  from  his  own 
experience,  indicates  the  following  mode  of  operation. 

A  horizontal  reverberatory  furnace*  is  generally 
adopted  at  the  present  time,  the  hearth  of  which  is 
made  of  a  cast-iron  dish,  10  to  12  centimetres  deep, 

I.  5  metres  in  length,  and  1.2  metres  wide,  and  several 
centimetres  thick.  The  furnace  is  so  constructed  that 
the  working  space  is  no  greater  than  is  necessary,  and 
the  arch  is  as  flat  as  it  is  possible  to  build  it.  The 
flue  from  the  fireplace  has  a  damper,  by  which  the 
flame  may  be  made  to  pass  into  an  opening  connected 
with  a  metallic  hood  and  chimney.  This  arrangement 
saves  the  men  from  being  annoyed  by  the  gases  and 
by  too  much  heat.  The  author  enlarges  on  the  advan- 
tage of  heating  by  gases,  by  which  oxidization  and 
ashes  are  prevented.  The  flame  may  even  be  made 
deoxidizing.  There  is  certainly  no  manufacturer 
who  has  not  observed  the  great  quantity  of  ashes 
deposited  after  twenty-four  hours  in  the  cast-iron 
dish  of  a  newly  heated  furnace,  especially,  when  the 
draft  is  good.    We  know  also,  how  deleterious  is  the 

*  These  furnaces,  notwithstanding  many  defects,  present  three 
important  advantages:  I.  There  is  a  considerable  economy  of  fnel; 

II.  The  work  is  easy  and  rapid.  Where,  in  other  furnaces,  4 
charges  were  a  day's  work,  in  these,  from  ^  to  8  charges,  each 
double  the  former  in  weight,  were  effected;  III.  The  furnaces  cost 
less  and  last  longer. — In  England,  where  fuel  and  iron  are  cheap, 
and  labor  liigh,  the  metallic  egg-shaped  furnaces  are  used,  and  the 
stirring  is  done  by  power.  No  other  but  carbonized  animal  sub- 
stances can  be  charged  there,  and  they  must  be  mixed  with  the 
potassa  in  the  furnace,  whereas  their  mixture  is  more  thorough  in 
revolving  cylinders. 


BLUE  COLORS. 


207 


action  of  these  ashes  upon  the  contents  of  the  bath, 
especially  when  peat  or  bituminous  coal  is  burned. 

With  a  furnace  of  the  above  construction,  the 
author  proposes  a  mode  of  operation,  which  has  already 
been  employed  in  several  works,  and  which  may  be 
described  as  follows:  The  charge  is  composed  of  100 
kilogrammes  of  potash,  two-thirds  of  which  is  from 
the  evaporated  mother  liquors,  and  one-third  of  fresh 
potash;  20  kilogrammes  of  animal  charcoal  obtained 
by  the  carbonization  of  substances  poor  in  nitrogen, 
and  the  nature  of  which  is  not  well  adapted  for  a  direct 
treatment;  from  65  to  70  kilogrammes  of  pure  animal 
matters,  as  dry  as  practicable ;  and  8  kilogrammes  of 
iron.  The  fire  is  urged  until  all  the  potash  is 
thoroughly  fused,  which  state  is  more  rapidly  reached 
with  the  aid  of  two  or  three  stirrings.  Then  the  ash 
pit  is  closed*  and  the  damper  turned  on  for  charging 
one-half  of  the  animal  charcoal.  The  fire  is  urged 
again,  and  the  stirring  is  continued  vigorously,  until 
the  mass  has  acquired  the  proper  consistency  and 
potassium  is  produced,  which  is  ascertained  by  the 
formation  of  blue  flames  of  oxide  of  carbon,  and  by  a 
peculiar  white  cloud  of  burning  vapor  of  potassium. 
In  this  state,  the  fused  mass  is  in  the  proper  state  for 
transforming  into  cyanogen  the  ammonia  disengaged 
from  the  animal  substances.  The  latter  are  then  put 
in,  those  richer  in  nitrogen  first,  but  not  in  large 
pieces  or  in  considerable  quantities,  which  would 
prevent  their  rapid  sinking  and  their  equal  distribu- 
tion in  the  bath,  and  would  produce  gas  too  rapidly 

*  When  the  furnace  is  heated  by  means  of  a  gas  generator,  a 
reducing  flame  will  be  obtained  by  diminishing,  or  stopping 
entirely,  the  entrance  of  the  air  necessary  to  complete  combustion. 


208 


MANUFACTURE  OF  COLORS. 


at  one  spot.  The  ammonia  will  not  have  time  to  be 
transformed.  When  the  65  to  70  kilogrammes  of 
dried  animal  substances  have  been  charged  in,  the 
mass  begins  to  be  hard  and  dry,  and  difficult  to  fuse. 
No  time  should  then  be  lost  in  adding  the  remainder 
of  the  animal  charcoal,  which,  being  in  a  fine  powder, 
is  more  readily  incorporated,  and  reduces  the  cyanide 
of  potassium  (cyanate  of  potassa?)  already  formed. 
Lastly,  after  another  thorough  stirring,  the  working 
door  is  closed  for  a  little  while,  and  the  contents  of 
the  furnace  are  rapidly  removed  intp  an  iron  vessel, 
which  is  immediately  covered. 

It  does  not  seem  advantageous  to  work  at  any  one 
time  with  charges  much  greater  or  less  than  the  indi- 
cated proportions ;  but  the  author  does  not  say  that 
these  numbers  are  the  only  correct  ones,  and  the 
manufacturer,  in  certain  cases,  will  do  well  to  modify 
them.  Mr.  Brunnquell  has  made  many  experiments 
for  the  purpose  of  establishing  to  a  certainty,  the 
composition  of  the  charges  in  the  ratio  of  the  nitrogen 
held  by  the  animal  substances ;  but  he  soon  found  out 
that  the  result  depended  upon  so  many  other  circum- 
stances, which  often  could  not  be  explained,  that  it  was 
impossible  to  establish  rules  adapted  to  all  modifica- 
tions. The  manufacturer  who  has  a  careful  foreman, 
who  can  be  trusted,  should  give  him  a  certain  liberty 
of  action  in  this  respect.  Practice  will  point  out  the 
time  when  the  charge  is  completed,  and  does  not 
require  any  new  additions ;  or  how  different  animal 
matters  should  be  treated.  Thus,  hair  and  leather 
waste  render  the  mass  hard  and  dry ;  whereas  with 
sinews,  rags,  etc.,  the  charge  remains  fluid  and  easily 
worked. 

Mr.  Brunnquell  remarks,  and  rightly  so,  that  the 


BLUE  COLORS. 


209 


value  of  the  raw  materials  is  not  in  a  direct  ratio  with 
their  per  cent,  of  nitrogen.  A  substance  with  twice 
as  much  nitrogen  as  another,  may  have  a  value  more 
than  double,  because  with  the  same  loss  of  potassa,  the 
same  labor,  and  the  same  consumption  of  fuel,  the 
production  of  ferrocyanide  is  much  greater.  Old  shoe 
leather  should  be  employed  with  moderation,  since 
the  author,  after  careful  washings,  ascertained  that  it 
contained  a  large  proportion  of  sand  and  other  impu- 
rities. 

In  regard  to  the  addition  of  iron  filings  or  turnings, 
Mr.  Brunnquell  states  that  it  does  not  increase  the 
yield,  but  saves  the  cast-iron  vessels  in  which  the 
operation  takes  place.  It  results  from  experiments 
made  by  Mr.  Fleck,  that  a  cast-iron  crucible  will 
stand  100  operations  without  the  addition  of  iron.  If 
the  latter  be  introduced  into  the  charges,  the  vessel 
will  last  through  from  350  to  400  operations.  The 
iron  tools  which  are  constantly  exposed  to  the  action 
of  the  fused  mass,  are  always  covered  with  a  coat  of 
sulphide  of  iron.  On  the  contrary,  the  iron  scraps  in- 
troduced during  the  operation,  have  scarcely  the  time 
to  be  transformed  into  sulphide  before  they  are  re- 
moved from  the  furnace. 

At  all  events,  the  whole  indicated  proportion  of 
iron  scraps  should  be  added  at  the  beginning  of  the 
operation,  with  the  animal  charcoal.  Certain  manu- 
facturers put  in  the  iron  scraps  during  the  last  period 
of  the  heat,  and  cannot  expect  to  save  their  crucibles 
and  cast-iron  hearths.  The  author  learned  that,  in  a 
German  establishment,  it  was  considered  as  very 
important  to  let  the  iron  scraps  become  oxidized 
beforehand ;  but  he  made  no  direct  experiment,  and, 
should  there  be  any  advantage  in  the  precaution,  it 
14 


210 


MA^fUFACTURE  OF  COLORS. 


would  be  more  simple  to  use  pure  spathic  iron  or  iron 
scales. 

Here  is  a  little  more  advice  on  the  manner  of 
treating  the  calcined  charges.  When  cold,  thej  are 
coarsely  broken,  then  digested  for  twenty-four  hours 
in  water  at  the  temperature  of  from  50°  to  60°  C.  with 
frequent  stirrings,  and  lastly,  boiled.  After  settling, 
the  liquor  is  decanted,  and  the  residue  is  washed  with 
water.  The  other  manipulations  present  no  ditSculty. 
The  main  point  is  the  manner  of  working  the  charge, 
and  a  peculiarity  of  this  manufacture  is,  that  it  is 
more  easy  to  obtain  a  good  product,  than  a  great  deal 
of  it.  The  only  difficulty  in  the  way  of  the  quality, 
is  the  separation  of  the  sulphate  of  potassa  from  the 
crude  ferrocyanide,  and  the  best  method  consists  in  a 
complete  reduction  during  the  calcination  of  the 
charge. 

The  process  which  we  are  going  to  describe,  and 
which  was  experimented  upon  by  the  author  conjointly 
with  Mr.  "Weber,  consists  in  transforming  ammonia 
into  cyanide  of  ammonium,  by  heating  the  former 
substance  with  charcoal  or  other  carbon  materials. 
A  distinguishing  feature  is  the  transformation  of  the 
cyanide  of  ammonium  thus  obtained,  into  cyanide  of 
potassium,  and  that  of  the  latter  into  ferrocyanide  by 
the  wet  way.  The  operation  consists  in  passing  the 
gases  and  ammonia,  produced  by  the  carbonization 
of  the  animal  substances,  through  tubes  holding  in- 
candescent charcoal.  The  ammonia  becomes  cyanide 
of  ammonium,  which  is  put  in  contact  with  an  aqueous 
solution  of  potassa  and  with  an  iron  compound.  The 
result  is  ferrocyanide  of  potassium.  Here  are  the 
principal,  ad  vantages  of  this  process  : — 

I.  There  is  no  great  loss  of  potassa,  and  the 


BLUE  COLORS. 


211 


expense  of  revivifying  this  alkali  is  entirely  done 
away  with; 

II.  It  is  possible  to  replace  potassa  by  soda,  which 
is  much  cheaper ; 

III.  It  is  possible  to  employ  bones,  the  residuary 
black  of  which  is  generally  sufficient  to  cover  the 
cost  of  the  bones  and  of  the  calcination.  Therefore, 
the  ammoniacal  gases  cost  nothing; 

IV.  It  is  possible  to  save  for  a  further  operation 
the  ammonia  which  has  escaped  transformation  into 
cyanide  during  the  calcination.  The  secondary  am- 
moniacal salts  may  also  be  utilized,  by  adding  them, 
with  a  certain  proportion  of  lime,  to  the  raw  materials. 

Several  questions  relating  to  the  process  of  manu- 
facture have  been  resolved  by  the  author,  as  follows : — 

1.  The  transformation  takes  place  without  difficulty, 
and  on  a  scale  sufficiently  large  to  base  upon  it  a 
system  of  preparation  of  cyanogen  compounds.  As  a 
proof  of  the  possibility  of  the  reaction,  we  may  cite  the 
production  of  the  cyanide  of  ammonium  from  ammonia 
and  carbonic  oxide,  or  from  the  gaseous  nitrogen 
oxide  and  alcoholic  vapor  under  the  influence  of 
spongy  platinum. 

2.  The  gases,  other  than  ammonia,  which  are  pro- 
duced at  the  same  time  during  the  carbonization,  are 
not  an  obstacle  to  this  process  of  manufacture. 

3.  The  transformation  of  the  cyanide  of  ammonium 
into  ferrocyanide  of  potassium,  is  effected  without 
loss. 

The  easiest  method  of  operating  this  transformation 
would  be  that  proposed  by  Mi*.  Binks,  that  is,  with 
an  aqueous  solution  of  potassa.  But  we  cannot  do 
so,  because  the  carbonate  of  potassa  is  not  decom- 
posed, either  by  hydrocyanic  acid  or  by  cyanide  of 


212 


MANUFACTURE  OF  COLORS. 


ammonium.'^  Caustic  potassa,  on  account  of  the 
excess  of  carbonic  acid  in  the  gases,  cannot  be  used. 
We  must,  therefore,  have  recourse  for  this  decompo- 
sition to  intermediary  substances,  and  the  author 
chooses  the  sulphate  of  protoxide  of  iron.  If  cyanide 
of  ammonium,  or  hydrocyanic  acid  and  carbonate  of 
ammonia,  be  passed  through  a  solution  holding  an 
excess  of  sulphate  of  iron,  sulphate  of  ammonia  and 
cyanide  of  iron  are  produced.  We  thus  obtain  a 
double  result:  first,  all  the  ammonia  is  collected  in 
the  state  of  sulphate,  which  pays  largely  for  the 
expense  of  the  iron  salt ;  second,  the  cyanide  of 
ammonium  is  instantaneously  transformed  into  an 
insoluble  and  fixed  compound,  which,  after  a  treat- 
ment with  the  carbonates  of  jDotassa  or  soda,  may 
furnish  a  ferrocyanide  of  either  of  these  bases. 

During  the  process  of  manufacture,  the  carboniza- 
tion is  effected  so  as  to  expel  all  the  nitrogen  in  the 
gaseous  form,  instead  of  preserving  it  in  the  carbona- 
ceous residuum,  as  in  former  methods.  If  bones  be 
employed,  the  quality  of  the  resulting  bone  black 
should  be  considered,  and  it  matters  little  whether  or 
not  a  small  percentage  of  nitrogen  remains  in  it.  We 

*  More  recently  the  author  has  made  several  direct  experiments 
which  clearly  prove  that  carbonate  of  potassa,  either  in  solution  in 
water,  or  at  a  high  temperature,  decomposes  cyanide  of  ammonium 
completely.  But,  as  he  has  never  been  able  to  realize  this  transfor- 
mation in  liis  experiments  on  a  large  scale,  and  has  alwa3^s  remarked 
that  hydrocyanic  acid  was  disengaged,  especially  when  the  alkaline 
liquors  were  boiled,  Mr.  Brunnquell  considers  this  fact  as  a  positive 
proof  that  carbonic  acid  has  intervened,  and  that,  instead  of  cyanide 
of  ammonium,  hydrocyanic  acid  (with  a  little  undecomposed  car- 
bonate of  ammonifi)  was  obtained.  Therefore,  theoretically  speak- 
ing, there  must  be  a  way  of  transforming  at  once  all  the  nitrogen 
into  cyanogen. 

I 


BLUE  COLOKS. 


213 


know  that  the  good  quality  of  bone  black  depends  on 
the  following  conditions:  the  bones  employed  should 
not  be  deprived  of  their  fat ;  the  carbonization  must 
be  complete,  and  effected  without  gaseous  pressure. 
When  other  raw  materials  are  used,  it  is  important 
to  obtain  all  the  niti-ogen ;  therefoi-e,  a  first  carboni- 
zation transforms  them  into  a  charcoal  easily  pul- 
verized, which  is  then  thoroughly  mixed  with  slaked 
lime,  and  calcined  again.  The  residue  is  a  very  good 
manure  or  compost. 

The  carbonizing  furnaces  are  disposed  like  those  of 
gas  works,  and  the  number  and  the  sizes  of  the  retorts 
are  made  to  suit  the  importance  of  the  manufacture. 
The  outlet  pipes  all  dip  into  a  common  horizontal  main, 
where  the  distilled  animal  oil  is  condensed,  and  there 
is  formed  a  hydraulic  joint,  which  produces  a  certain 
pressure.  All  the  products  thus  become  mixed  before 
they  reach  the  calcining  tubes  made  of  fire  clay.  There 
is  also  the  advantage  that  the  flow  of  gases  is  quite 
regular,  because  the  small  volume  of  gases  produced 
by  a  retort  at  the  end  of  the  distillation,  is  counter- 
balanced by  the  large  volume  of  gases  issuing  from 
another  retort  which  has  been  recently  charged.  If 
we  suppose  that  three  retorts  are  employed,  and  that 
the  carbonization  of  a  charge  lasts  six  hours,  one  retort 
will  be  filled  every  two  hours.  The  pipes  connecting 
with  the  hydraulic  main  should  be  provided  with 
stopcocks  in  case  an  accident  should  happen.  They 
should  also  be  at  least  six  centimetres  in  diameter, 
short,  and  easy  of  access  in  every  direction. 

The  transformation  of  the  ammonia  into  cyanide  of 
ammonium  takes  place  when  the  gases  pass  through 
the  fire-clay  pipes,  which  are  heated  to  an  intense 
red  heat,  and  filled  with  wood  charcoal,  broken  into 


214 


MANUFACTURE  OF  COLORS. 


pieces  of  the  size  of  walnuts.  Numerous  trials  have 
proven  that  iron  pipes  cannot  be  used  for  this  purpose, 
because,  when  cyanide  of  ammonium,  or  hydrocyanic 
acid,  or  cyanogen  are  brought  into  contact  with  iron 
at  a  red  heat,  they  split  into  their  elements,  and  form 
a  carbide  of  iron.  In  three  experiments  made  with 
gunbarrels,  not  a  trace  of  cyanide  of  ammonium  was 
found.  The  author  tried  to  employ  in  this  manu- 
facturing process,  an  iron  cylinder,  by  protecting  its 
inside  with  a  carbonaceous  surface  obtained  by  the 
calcination  of  several  coats  of  tar.  But  the  results 
of  the  working  operation  were  far  from  satisfactory, 
since  the  yield  was  but  4  per  cent.  This  was  possibly 
due  to  the  fact  that  he  had  not,  at  that  time,  ascer- 
tained the  great  proportion  of  carbonic  acid  contained 
in  the  gases;  and  that  the  caustic  potassa,  intended  for 
the  absorption  of  the  cyanide  of  ammonium,  had  been 
transformed  into  carbonate,  and  even  bicarbonate. 
The  best  process  for  protecting  the  iron  tubes  was 
found  to  be  several  coats  of  a  mixture  of  clay  and  ox 
blood,  gently  heated  after  each  successive  coat. 
During  the  first  experiments  with  sulphate  of  iron, 
instead  of  a  solution  of  potassa,  too  much  heat  was 
applied,  and  the  iron  pipes  were  burned.  Although  it 
does  not  appear  entirely  impossible  to  use  metallic 
pipes,  those  made  of  fire  clay  seem  to  be  preferable  in 
every  respect.  These  pipes  have  a  smaller  diameter 
than  the  retorts,  and  their  extremities  are  so  disposed 
as  to  receive  cast-iron  joints.  The  smaller  their  diame- 
ter and  the  greater  their  length,  the  better  it  is  for  the 
operation.  Those  used  by  the  author  were  10  centi- 
metres in  diameter  and  2  metres  long.  The  internal 
disposition  of  the  furnace  is  also  that  of  furnaces  for 
gas  retorts,  where  the  greatest  possible  number  of 


BLUE  COLORS. 


215 


retorts  are  to  be  heated  throughout  their  whole  length, 
with  the  smallest  consumption  of  fuel.  A  very  good 
furnace  is  that  of  Croll  for  gas,  with  the  combined 
employment  of  clay  and  cast-iron  retorts. 

With  this  disposition  it  has  been  possible  to  heat 
seven  retorts  and  seven  pipes  with  one  fireplace. 
The  filling  of  the  pipes  with  charcoal  is  not  absolutely 
necessary,  because  the  other  gases  accompanying  the 
ammonia  may  furnish  the  carbon  for  the  cyanogen ; 
but  charcoal,  on  account  of  its  porousness,  aids  in  the 
transformation.  The  extremities  of  the  pipes  are 
closed  with  perforated  disks  of  fire  clay,  which  pre- 
vent the  joints  from  becoming  obstructed.  Before 
the  gases  are  allowed  to  pass  through,  the  pi]3es 
should  be  of  an  intense  red  heat.  In  addition  to  the 
ordinary  losses  of  manufacture,  there  are  undecom- 
posed  tarry  vapors,  which  dirty  the  liquors.  A  very 
intense  red  heat  is  the  temperature  necessary  for  the 
formation  of  cyanogen.  As  in  previously  described 
processes,  the  yield  depends  on  regularly  conducted 
operations. 

We  have  seen  that  the  transformation  of  the  cya- 
nide of  ammonium  into  cyanide  of  potassium,  and 
then  into  ferrocyanide  of  potassium,  is  effected  by  the 
intermediation  of  the  sulphate  of  iron.  The  only  diffi- 
culty in  the  practical  operation  is  to  arrive  at  a  com- 
plete absorption  of  the  cyanide  of  ammonium  in  the 
solution  of  sulphate  of  iron,  and  that  without  a  strong 
pressure  of  gases,  which  not  only  impairs  the  quality 
of  the  bone  black,  but  causes  losses  of  a  portion  of  the 
gases  through  leaks  in  the  apparatus.  The  author 
uses,  for  this  purpose,  apparatus  which  is  very  simple 
and  permits  of  regulating  at  will  the  rapidity  of  the 
operation.   Let  us  suppose  a  box,  about  2  metres  long, 


216 


MAXtJFACTURE  OF  COLORS. 


60  centimetres  wide,  and  20  centimetres  deep,  in  which 
are  placed  four  flat,  shallow  pans,  5  centimetres  high, 
and  pat  one  on  top  of  the  other  in  an  inverted  posi- 
tion (Fig.  47).  On  the  bottom  of  each  pan,  towards 
one  of  the  ends,  there  is  a  narrow  opening.   The  box  is 


Fig.  47. 


filled  with  the  liquor,  and  the  mixture  of  gases,  which  is 
introduced  below  the  first  pan,  expands  until  it  gains 
the  opening.  It  then  passes  into  the  second  pan,  and, 
in  the  same  manner,  into  the  third  and  fourth.  Theo- 
retically speaking,  there  is  constantly  a  layer  of  gases, 
of  4  X  1.20  metres  =  4.80  square  metres  in  area,  in 
contact  with  the  liquid,  and  the  distance  followed  by 
the  gases  is  4x  2  metres  =  8  metres,  under  a  pressure 
of  only  0.20  metre  of  water.  The  box  is  also  provided 
with  a  stopcock  for  removing  the  liquors,  a  funnel 
which  dips  a  little  below  the  level  of  the  liquid,  and 
an  outlet  pipe  for  the  washed  gases,  which  are  after- 
wards burned  under  the  fireplace.  In  order  to  pre- 
vent explosions  the  gases  to  be  burned  are  made  to 
pass  through  a  small  box  filled  with  fine  metallic  gauze. 
Should  a  precipitate  take  place  in  the  liquors,  it  is 
recommended  to  employ  a  stirring  apparatus  with 
blades  in  each  compartment  of  the  box,  and  the  ver- 
tical shaft  of  which  passes  through  a  stuffing-box. 
In  the  figure,  a  a  is  the  pipe  which  conducts  the 


BLUE  COLORS. 


217 


gases  into  the  box ;  a,  sheet-iron  box ;  h  h  h  sheet- 
iron  inverted  pans  ;  c  c,  handles  for  moving  the  pans  ; 
(Z,  funnel;  /,  outlet  pipe  for  the  gases;  x  level  of 
the  liquor. 

Instead  of  a  large  absorbing  apparatus,  it  will  be 
more  advantageous  to  employ  two  smaller  ones,  so 
disposed  as  to  pour  the  liquors  from  one  into  the 
other.  In  this  manner  the  sulphate  of  iron  will  be 
entirely  precipitated  without  loss  of  cyanide  of  ammo- 
nium. The  liquor  running  from  the  first  box  will, 
therefore,  hold  only  sulphate  of  ammonia  in  solution, 
cyanide  of  iron  in  suspension,  and  a  small  proportion 
of  hydrated  oxide  and  sulphide  of  iron.^  The  sul- 
phate of  ammonia  is  separated  from  the  filtered 
liquors  by  evaporation,  and  is  sold  to  the  alum 
makers,  or  is  mixed  with  lime  and  animal  substances 
for  the  production  of  cyanogen.  The  precipitate  of 
cyanide  of  iron  is  boiled  with  potassa  and  transformed 
into  ferrocyanide.  Lastly,  the  residues  of  iron  are 
either  thrown  away,  or  dissolved  in  hydrochloric  acid, 
to  be  used  instead  of  sulphate  of  iron. 

There  is  no  difficulty  in  the  preparation  and  crys- 
tallization of  the  ferrocyanide  of  potassium,  because 
the  materials  employed  are  quite  pure.  If  the  iron 
precipitate  has  been  sufficiently  washed,  and  then 
boiled  with  a  solution  of  purified  potassa,  the  liquors 
contain  but  a  small  proportion  of  carbonate  of  potassa, 
besides  the  ferrocyanide.  The  author  believes  that 
soda  may  be  employed,  and  experiments  on  a  large 
scale  have  furnished  a  pure  yellow  ferrocyanide  of 

*  For  the  preparation  of  300  parts  of  ferrocyanide  of  potas- 
sium, we  need  187.3  parts  of  cyanide  of  ammonium.  The  latter 
requires  for  its  formation  600  parts  of  sulphate  of  iron,  and  pro- 
duces 243  parts  of  sulphate  of  ammonia. 


218 


MANUFACTURE  OF  COLORS. 


sodium,  but  iu  small  crystals.  The  iron  deposit  left 
after  the  treatment  with  the  alkalies,  should  be  washed 
and  drained.  The  washings  are  kept  for  making 
fresh  solutions  of  potassa.  The  mother  liquors  are 
also  put  to  the  same  use. 

If  we  compare  the  old  and  the  new  processes,  we 
find : — 

First,  that  in  the  latter  there  is  a  saving  of  labor. 
The  fusion  of  the  potassa  and  animal  matters,  which 
requires  two  workmen,  is  entirely  avoided,  and  one 
workman  is  sufficient  for  two  carbonizing  furnaces 
and  a  great  many  clay  pipes,  since  these  require  to  be 
opened  but  once  every  two  or  three  days  for  the  pur- 
pose of  adding  a  little  charcoal.  The  labor  required 
for  the  treatment  by  the  sulphate  of  iron  is  much 
less  than  that  required  for  lixiviating  the  carbonized 
cakes  of  raw  materials.  Moreover,  the  labor  entailed 
by  the  revivification  of  the  salts  of  the  mother  liquors 
is  entirely  obviated. 

Second,  the  consumption  of  fuel  in  the  new  process 
is  somewhat  greater,  because  the  formation  of  the 
cyanogen  is  slower.  But,  supposing  that  the  con- 
sumption be  double,  this  inconvenience  is  more  than 
counterbalanced  by  the  advantages  of  the  method. 

It  is  acknowledged  that  the  process  presents  cer- 
tain difficulties,  which  may,  however,  be  overcome;  but 
the  great  saving  in  potassa,  and  the  possibility  of  sub- 
stituting soda  for  it,  are  very  important  economical 
results. 

In  concluding,  the  author  remarks  that  the  method 
he  proposes,  that  is,  the  production  of  the  cyanogen 
before  its  combination  with  the  fixed  alkalies,  may 
possibly  lead  to  the  employment  of  atmospheric  air. 
During  the  experiments  made  on  the  production  of 
cyanogen  from  the  nitrogen  of  the  air,  MM.  "Woehler, 


BLUE  COLORS. 


219 


El'dmann,  and  Marchand  have  remarked  that  this 
preparation  succeeds  only  in  the  presence  of  steam  or 
of  hydrate  of  potassa.  This  observation,  and  other 
analogous  ones,  have  caused  many  chemists  to  sup- 
pose that  there  was  always  a  formation  of  ammonia. 
Direct  experiments  have  also  proven  the  production 
of  ammonia  from  nitrogen  and  steam  in  contact  with 
red-hot  charcoal.  Mr.  Fleck  has  communicated  to 
the  author  the  results  of  such  experiments,  by  which 
he  obtained  quite  a  large  proportion  of  ammonia;  but 
in  several  cases,  and  without  ascertained  causes,  no 
ammonia  was  formed.  It  seems  that  this  mode  of 
formation  should  be  studied  more  thoroughly,  and 
directly,  that  is,  for  instance,  by  mixing  with  nitro- 
gen, variable  measured  i3roportions  of  steam,  and 
then  transforming  the  ammonia  thus  produced  into 
cyanide  of  ammonium  by  the  process  indicated.  We 
shall  thus  avoid  most  of  the  practical  difficulties  up  to 
the  present  time  encountered,  in  the  preparation  of 
the  cyanide  of  potassium  from  the  nitrogen  of  the 
air,  for  instance,  among  others,  that  of  the  rapid  de- 
struction of  the  clay  pipes  by  the  fused  potassa. 

3cl.  Karmrodt  Process. 

In  the  Bulletin  of  the  Society  for  the  Advancement 
of  Arts,  Berlin,  1857,  there  is  a  memoir  of  Mr.  C. 
Karmrodt  upon  the  ferrocyanide  of  potassium  and  its 
manufacture  by  a  new  process,  which  we  shall  repro- 
duce in  part. 

The  author  points  out  the  destructive  action  of  the 
vapors,  disengaged  from  wood  and  animal  substances, 
upon  the  cyanide  of  potassium  in  the  nascent  state, 
and  states  that  experiments  made  with  charges  of 
250  kilogrammes  of  potassa  and  250  kilogrammes  of 


220  MANUFACTURE  OF  COLORS. 

the  substances  mentioned  below,  gave  the  following 

yields  in  ferrocyanide  of  potassium  : — 

10  charges  with  woollen  rags,  15.22  per  cent,  of  ferrocyanide. 

10     "         "    horn  waste,  16.26 

10      "         "    cow's  hair,  11.94       "  " 

10     "         "    leather  waste,         13.52       "  " 

10     "         "    good  charred  horn,  16.23  "  . 

10     "         "    woollen  rags,  n.57       "  " 

Showing  that  only  from  one-seventh  to  one-third  of 
the  nitrogen  present  in  the  raw  materials  was  utilized. 
Mr.  Karmrodt  demonstrates  the  advantages  resulting 
from  the  previous  carbonization  of  the  raw  substances, 
and  then  passes  on  to  the  description  of  his  new  pro- 
cess for  the  manufacture  of  ferrocyanide  of  potassium, 
as  follows : — 

In  order  to  combine  in  the  most  advantageous 
manner  the  production  of  the  cyanide  cf  potassium 


Fig.  48. 


with  ammoniacal  gases,  and  the  working  of  the  charge 
with  the  nitrogenized  charcoal,  I  have  invented  the 


BLUE  COLORS. 


221 


furnace  which  is  represented  in  the  vertical  section 
in  Fig.  48. 

The  cast-iron  cylinder  A,  for  calcining,  is  1.20  me- 
tres long  and  0.15  metre  in  diameter  on  top,  the  lower 
portion  being  a  little  larger.  Its  thickness  is  25 
millimetres,  and  it  carries  four  tubes,  a,  c,  cZ,  cast 
with  it,  5  centimetres  in  diameter  and  from  36  to  40 
in  length.  The  tube  or  pipe  h  is  connected  by  flange 
joints  and  another  small  pipe,  with  the  carbonizing 
vessel  B,  which  is  pear-shaped,  and  about  30  centi- 
metres in  diameter.  The  pipe  d  penetrates  the  brick 
flue  e,  which  continues  around  the  vessel  b,  and  ends 
atj^.  The  other  pipes  a,  c,  are  employed  for  cleaning 
those  which  are  opposite,  and  are  generally  closed 
with  a  plug  of  clay.  The  carbonizing  vessel  B,  and 
the  calcining  cylinder  a,  are  both  closed  with  a  cover 
which  may  be  made  gas  tight.  Under  the  cylinder, 
there  is  a  square  iron  frame  in  which  the  register  g 
slides  horizontally.  At  about  30  centimetres  above, 
there  is  also  an  annular  grate  li  li. 

When  the  calcining  cylinder  is  charged  with  alka- 
lized charcoal,  it  is  heated  with  a  charcoal  fire.  Some 
time  afterwards,  the  space  i  i  is  closed  with  an  iron 
cover,  and  the  di'aft  takes  place  through  a  flue  placed 
under  the  pipe  Z),  which  thus  establishes  a  heating 
system  common  to  A  and  b.  When  the  calcining 
cylinder  a  has  been  brought  to  a  red  heat,  the  animal 
substance  is  quickly  introduced  into  the  carbonizing 
vessel  B,  which  is  immediately  closed  with  its  cover 
luted  on.  The  gases  produced  by  the  carbonization 
escape  through  the  pipe  pass  through  the  whole 
length  of  the  cylinder  a,  and  coming  out  at  are 
burned  under  the  vessel  b,  and  increase  its  tempera- 
ture considerably.    By  this  disposition,  all  the  pro- 


222 


MANUFACTURE  OF  COLORS. 


ducts  of  the  combustion  of  the  fuel  and  of  the  carbon- 
ization of  the  animal  matters,  are  expelled  through 
the  flue  and  go  to  the  chimney,  or  are  utilized  for 
evaporating  the  liquors.  'No  disagreeable  smell  is 
disengaged  and  the  carbonizing  operation  lasts  from 
three-quarters  of  an  hour  to  one  hour  and  a  quarter. 

When  the  carbonization  is  completed,  and  when 
the  gases  passing  through  the  cylinder  have  formed 
a  certain  portion  of  cyanide  of  potassium,  the  register 
g  is  removed,  and  the  contents  of  a  fall  into  a  sheet- 
iron  box  placed  below,  and  which  is  closed  tight. 
After  cooling,  the  materials  are  thrown  into  water  by 
small  portions  at  a  time,  because,  should  all  the  char- 
coal saturated  with  cyanide  of  potassium  be  thrown 
at  once  into  the  water,  the  elevation  of  temperature 
would  be  such  as  to  decompose  a  large  portion  of  the 
cyanide. 

The  water  is  then  slowly  heated  up  to  from  75°  to 
80°  C,  and  the  charcoal  is  separated  from  the  solution 
by  means  of  a  metallic  sieve.  A  well-washed  char- 
coal may  be  used  for  another  operation,  or  it  is  used 
as  fuel,  and  its  ashes  are  carefully  lixiviated,  because 
they  are  rich  in  potassa. 

The  alkalized  charcoal  is  prepared  as  follows:  In 
an  iron  kettle,  20  parts  of  good  Russian  potash  are 
dissolved  in  10  parts  of  water,  and  there  is  mixed  in 
it  the  wet,  but  washed,  precipitate  resulting  from  the 
mixture  of  8  parts  of  sulphate  of  iron  and  6  parts  of 
potash.  30  parts  of  charcoal,  broken  to  the  size  of  a 
filbert,  are  then  stirred  with  the  mixture,  and  the 
whole  is  dried  at  a  moderate  temperature.  Coke 
may  be  cheaper  than  charcoal,  but  the  lixiviation  re- 
quires more  water,  and  its  ashes  have  scarcely  any 
value.    The  sulphate  of  potassa  resulting  from  the 


BLUE  COLORS. 


223 


precipitation  of  the  sulphate  of  iron,  is  used  in  the 
manufacture  of  alum. 

Mr.  Karmrodt  has  made  experiments  with  the  fur- 
nace above  described,  and  the  results  are: — ■ 


I.  By  using  each  time  L5  kilogrammes  of  Carbonate  of  Am- 
monia {crude  and  yielding  21  per  cent  of  Nitrogen). 


Ferrocyanide  of  -potassium  obtained 
with  the  carbonate  of  ammonia. 


Utilized  nitrogen. 


,  Per  1.5  kilog. 

L  0.500  kilog. 

2.  0.625  " 

3.  0.562  " 


Per  cent. 

33.3  per  cent. 
4L5  " 
37.5  " 


Per  cent.  Approximately. 

31.74  per  cent.  \ 
39.68  "  f 
35.71      "  \ 


The  greater  proportion  of  assimilated  (utilized) 
nitrogen  in  tliese  experiments,  in  comparison  with 
the  results  obtained  with  gunbarrels,  is  possibly  due 
to  the  greater  surface  of  reacting  substances,  and  to 
the  pressure  of  the  gases  during  their  passage. 


II.  With  Animal  Substances. 

The  alkalized  charcoal  of  these  experiments  was 
prepared  with  15  kilogrammes  of  horn  charcoal 
(yielding  7  per  cent,  of  nitrogen),  and  10  kilogrammes 
of  potash.  After  the  addition  of  the  washed  precipi- 
tate resulting  from  4  kilogrammes  of  sulphate  of  iron 
with  3  kilogrammes  of  potassa,  the  dried  mixture 
weighed  22  kilogrammes. 

In  each  operation  there  were  5  kilogrammes  of  this 
alkalized  charcoal,  corresponding  to  3.4  kilogrammes 
of  horn  charcoal,  placed  in  the  calcining  cylinder; 
and  it  received  the  gases  produced  in  the  carbonizing 
vessel  from  1.5  kilogrammes  of  horn  (yielding  16  per 
cent,  of  nitrogen). 


224 


MANUFACTURE  OF  COLORS. 


The  nitrogen  employed  was  therefore : — 

a.  In  the  alkalized  charcoal  .  .  .  238  orrammes. 
6.  In  the  raw  horn  to  be  carbonized       .  240 


478 


which  should  have  produced  altogether  2.39  kilo- 
grammes of  ferrocyanide  of  potassium. 

Ferrocyani/le  of  potassium  Utilized  nitrogen. 

obtaineii  toitJi  ,  >■  . 


1.5  kilog.  of  horn.  Per  cent.  Approximatively. 

1.  770.31  grammes.  32.4  \ 

2.  664.06       "  27.9  \ 

3.  712.50       "  30.0  i 


In  these  experiments,  there  remained  in  the  car- 
bonizing vessel  1.203  kilogrammes  of  horn  charcoal, 
which,  after  fusion  with  potassa,  gave  109.37  grammes 
of  ferrocyanide  of  potassium.  To  sum  up,  the  results 
were : — 

1.  770.31  grammes  of  ferrocyanide  =  154.06  grammes  of  nitrogen. 

2.  664.06  "  =122.81 

3.  712.50  "  ==142.50  " 

4.  109.37  "  =  20.31  " 


2256.24  "  =439.68  " 

whereas  the  whole  of  the  nitrogen  employed  was  3 
X  478  =  1434  grammes. 

III.  wall  Animal  Substaiices,  and  the  Alkalized  Charcoal  of  30 
kilogrammes  of  Wood  Charcoal^  20  of  Russian  Potash^  and 
the  Precipitate  of  i  kilogrammes  of  Sulphate  of  Iron  hy  ^  'of 
Potash. 

In  each  operation,  there  were  used  5  kilogrammes 
of  alkalized  charcoal,  upon  which  were  passed  the 
gases  of  1.5  kilogrammes  of  raw  horn.  The  results 
were : — 


BLUE  COLORS. 


225 


1.  5T4.22  grammes  of  feiTocyanide 

2.  4riL00  " 

3.  457.03  " 

4.  156.25*  " 


=  114.84  grammes  of  nitrogen. 
=  92.19  " 
=  91.41 

=  31.25  " 


1648.50  "  =329.69 

The  whole  quantity  of  horn  employed  was  4.5  kilo- 
grammes =  620  grammes  of  nitrogen.  We  see  there- 
fore, that  in  this  series  of  experiments,  the  proportion 
of  nitrogen  utilized  is  about  one-half  of  the  whole. 

!Now,  if  we  suppose  that  in  the  second  series  of 
experiments  with  animal  alkalized  charcoal  and  the 
same  quantity  of  horn  as  in  the  third  series,  there 
were  produced  as  much  ferrocyanide  of  potassium  as 
in  the  latter  case,  it  would  result  that  the  overplus  of 
38.4  parts  of  ferrocyanide  is  due  to  the  alkalized 
animal  charcoal.  , 

If  we  compare  together  the  yields  which  should  be 
obtained,  we  find  that,  with  the  alkalized  animal 
charcoal,  about  |  of  the  nitrogen  is  utilized.  Indeed, 
10.2  kilogrammes  of  horn  charcoal  (at  7  per  cent,  of 
nitrogen)  contain  710  grammes  of  nitrogen,  which 
should  have  produced  3580  grammes  of  ferrocyanide 
of  potassium,  while  the  result  was  only  600  grammes.f 

*  This  ferrocyanide  comes  from  the  treatment  of  the  charcoal 
left  by  the  carbonization  of  4.5  kilogrammes  of  raw  horn,  in  three 
operations. 

f  Although,  from  the  numbers  admitted  b}'  Mr.  Karmrodt,  it 
would  seem  that  the  yields  have  been  really  those  obtained  at  the 
end  of  the  operation,  we  should  remark  that  in  the  most  careful 
mode  of  working,  there  are  always  losses  which  cannot  be  avoided, 
and  which  are  sometimes  due  to  unknown  causes.  The  proportions 
of  nitrogen  indicated  for  various  animal  substances  are  average 
numbers.  In  order  to  facilitate  the  calculation,  it  has  been  as- 
sumed that  ferrocyanide  of  potassium  contains  20  per  cent,  of 
nitrogen,  whereas  the  real  proportion  is  19.87  per  cent. 

15 


226 


MANUFACTURE  OF  COLORS. 


Although  this  method  for  the  manufacture  of  fer- 
rocyanide  of  potassium  is  far  from  the  desired  per- 
fection, we  must  admit,  from  the  experiments,  that 
it  presents  several  advantages  over  the  usual  pro- 
cesses : — 

1.  A  greater  proportion  of  nitrogen  is  utilized. 

2.  The  liquors,  and  the  resulting  commercial  salt, 
are  less  impure  than  when  the  ordinary  process  of 
fusion  is  followed. 

3.  The  loss  of  alkaline  salts  is  small,  while  it  is 
considerable  in  the  method  by  fusion. 

4.  The  residues  are  small. 

A  manufacturing  establishment,  working  by  this 
method,  should  have  several  furnaces  of  the  pattern 
indicated,  since  the  daily  production  of  one  furnace 
is  only  twelve  kilogrammes  of  ferrocyanide  of  po- 
tassium. 

It  is  possible  to  increase  the  dimensions  of  the 
apparatus,  and  to  put  four  cylinders  in  one  furnace, 
so  as  to  produce  fifty  kilogrammes.  A  cheaper  fuel 
than  charcoal  may  be  employed,  and  burned  in  a  fire- 
place common  to  the  four  cylinders. 

4th.  Schinz  Process. 

In  the  apparatus  of  Mr.  C.  Schinz,  cyanide  of  po- 
tassium is  formed  by  the  contact  of  potassa  with 
nitrogen,  or  with  the  products  of  the  distillation  of 
nitrogenized  substances  in  closed  vessels. 

Figs.  49,  50,  and  51  represent  the  apparatus,  a, 
feeding  cast-iron  cylinder  placed  on  top  of  the  appa- 
ratus, and  closed  tight  with  the  cover  h.  c  c,  cast-iron 
plate  supporting  a,  and  perforated  with  a  hole  corre- 
sponding to  the  diameter,  in  the  clear,  of  the  cylin- 
der.   Underneath  is  an  iron  frame  in  which  slides 


BLUE  COLORS. 


227 


a  register  or  damper  e,  having  a  hole  e\  which  may 
be  made  coincident  or  not  with  the  opening  of  the 
lower  plate.  This  damper  is  moved  by  an  arrange- 
ment/of rack  and  pinion. 


Fiir.  50. 


Fig.  51. 


The  lower  part  of  this  iron  frame  covers  a  flue  ^, 
which  communicates  through  a  circular  grate  with  a 
vertical  retort  7i,  placed  immediately  below  the  open- 
ing already  mentioned.  The  circular  grate  is  mova- 
ble, in  order  to  be  cleaned  when  necessary. 

The  furnace  is  placed  under  the  flue  g  and  from 
tliis  flue  and  through  the  sides  i  ^,  of  the  furnace, 
there  are  two  gas  pipes  i'  i\  one  on  each  side. 

The  vertical  retort  h  is  made  of  sheet  iron,  and  is 
enclosed  in  sand  kept  in  a  special  space,  so  that  the 
retort  may  expand  and  contract  when  heated  or  cooled. 
The  fireplace,  which  is  lined  w^ith  fire-bricks,  is  placed 
around  the  lower  part  of  the  retort,  and  is  separated 


228 


MAXUFACTURE  OF  COLOTIS. 


from  the  sand  by  a  cylinder  h  of  refractory  clay. 
The  retort  li  is  supported  by  another  flue  I  I,  similar 
to  g  and  is  connected  by  means  of  a  grate  with 
another  cylinder  m,  which  is  immediately  below  the 
retort  7i,  but  has  a  diameter  a  little  larger.  The 
cylinder  m  receives  the  substances  delivered  into  it, 
and,  being  hermetically  closed,  protects  them  from 
contact  with  the  air  while  they  are  cooling  off.  It  is 
supported  by  a  rectangular  box  n  in  which  moves, 
by  rack  and  pinion,  a  piston  which  closes  or  opens 
the  aperture  o,  placed  sideways  of  the  axis  of  the 
apparatus.  The  receiver  rolls  on  small  wheels,  and 
its  top  fits  close  to  the  piston-box  nn.  A  cylindrical 
metallic  sieve  r  may  be  put  in,  or  removed  from  the 
receiver  by  means  of  handles.  A  system  of  levers 
raises  the  rails  r'  r\  and  causes  the  receiver  to  be 
firmly  pressed  against  the  box  n  n. 

The  mode  of  operation  is  as  follows :  the  feeding 
cylinder  a  is  filled  with  pieces  of  wood  charcoal  or 
coke,  of  the  size  of  a  walnut,  which  are  mixed  with  a. 
certain  proportion  of  dried  potassa  and  filings  or  oxide 
of  iron.  The  cover  h  is  put  on,  and  the  damper  e  is 
made  to  slide  by  means  of  the  rack  and  pinion,  so 
that  the  charge  put  in  a  falls  into  the  retort  /?.  The 
diameters  of  the  cylinders  a,  ^,  and  m  increase  succes- 
sively in  size,  and  the  substances  acquire  a  conical 
shape,  which  is  advantageous  to  the  regular  flow  of 
gases  and  prevents  the  obstruction  of  the  grates. 

The  nitrogenized  gases  come  into  the  retort  by  the 
gas  pipes.  The  formation  of  the  potassium  takes 
place  only  in  that  portion  of  the  retort  which  is  sur- 
rounded by  fire ;  but,  as  by  its  volatility  this  metal 
rises  upwards,  it  meets  its  nitrogen  gas  and  is  trans- 
formed into  cyanide  of  potassium.   These  dispositions 


BLUE  COLORS. 


229 


aid  the  chemical  action,  and  there  is  no  loss  of  po- 
tassium by  volatilization.  The  remainder  of  the  gases 
escape  through  the  lower  grate  and  flue,  but  not  be- 
fore they  have  passed  through  a  mass  of  materials 
sufficient  to  transform  the  whole  of  the  nitrogen  into 
cyanogen.  If  the  materials  contained  in  the  retort 
are  in  a  pulverulent  state,  the  flow  of  the  gases  may  be 
aided  by  an  exhauster,  similar  to  those  used  in  gas 
works. 

When  the  operation  has  been  continued  long  enough 
for  the  production  of  a  certain  quantity  of  cyanide  of 
potassium,  the  sliding  damper  o  is  opened,  and  a 
portion  of  the  product  is  made  to  fall  into  the  receiver 
q,  A  fresh  charge  is  then  put  into  a,  and  the  opera- 
tion continues  in  the  manner  already  explained.. 

The  apparatus  may  be  modified  for  distilling  nitro- 
genized  substances,  by  removing  the  lower  grate  and 
flue. 

The  advantages  of  this  apparatus  are : — 

1.  An  economy  of  fuel,  because  a  portion  of  the 
heat  generally  lost  is  here  used. 

2.  A  saving  of  potassa  or  its  combinations,  because 
the  special  disposition  of  the  apparatus  prevents  its 
volatilization. 

3.  A  saving  of  nitrogenized  substances,  on  account 
of  the  large  surfaces  presented  by  the  reacting  sub- 
stances, and  because  the  reaction  takes  place  in  closed 
vessels. 

4.  An  increased  yield,  resulting  from  the  above 
causes,  and  because  the  products  are  protected  from 
the  contact  of  the  air,  until  they  are  sufficiently  cold, 
and  until  there  is  no  longer  any  danger  of  the  cya- 
nogen being  transformed  into  cyanic  acid.  Moreover, 


230 


MANUFACTURE  OF  COLORS. 


the  cyanogen  gas  is  free  from  all  compounds  of  sul- 
phur and  phosphorus. 

5.  A  saving  of  labor,  since  the  operation  is  con- 
tinuous, and  is  effected  with  mechanical  appliances. 

5th.  Determination  of  the  Value  of  the  Fused  Materials. 

It  is  an  old  complaint,  says  Mr.  Brunnquell, 
that  the  manufacture  of  ferrocyanide  of  potassium 
is  so  backward,  notwithstanding  the  progress  of 
chemistry  applied  to  the  arts.  Indeed,  in  the  best 
managed  works,  the  yield  is  only  one-third  of  what  it 
should  be,  and  the  remainder  of  the  materials  are  en- 
tirely destroyed  or  valueless.  Moreover,  few  of  the 
recent  processes  have  been  adopted ;  and  the  manu- 
facture by  the  nitrogen  of  the  air,  experimented  upon 
in  France  and  in  England,  has  been  abandoned.  It 
appears,  therefore,  that  the  old  process  is  still  gener- 
ally practised,  and  manufacturers  should  endeavor 
to  work  it  to  the  best  advantage.  It  is  highly  im- 
portant to  determine  the  truth  relative  to  certain 
questions,  which  have  often  been  put  forward,  but 
never  settled  in  a  satisfactory  way;  for  instance, 
whether  it  is  preferable  to  employ  carbonized,  or 
simply  dried  animal  substances ;  whether  the  po- 
tassa  should  be  previously  mixed  with  the  animal 
matters,  or  the  latter  added  only  when  the  potassa 
is  melted ;  whether  the  fusion  should  be  rapid  and 
effected  under  a  high  temperature,  or  slow  and  at  a 
low  temperature,  etc.  There  remain  also  to  be  decided 
whether  purified  potassa  is  preferable ;  whether  the 
greater  yield  obtained  in  closed  vessels  is  not  more 
than  counterbalanced  by  the  greater  cheapness  of  the 
open  apparatus,  and  the  greater  facility  of  working, 
etc.    Lastly,  we  should  determine  the  best  propor- 


BLUE  COLORS. 


231 


tions  between  the  potassa  and  the  other  materials. 
As  an  example  of  the  doubt  still  left  on  these  points, 
we  shall  give  a  few  receipts. 

1.  MM.  Ha3fflmayer  anii  Priickner,  in  1837,  gave 
the  following  proportions  : — 

100  kilogrammes  of  blood  for  28  to  30  kilogrammes  of  potassa. 
100  "  horn       "  33  to  35  "  " 

100  "  leather   "  45  to  48  "  " 

That  is  to  say,  the  less  potassa,  as  the  substances  are 
richer  in  nitrogen,  while  it  should  be  the  opposite. 

2.  Mr.  Gen  tele,  in  1837,  also  gave  certain  propor- 
tions (TecJinologiste,  vol.  xii.  p.  240)  : — 

For  65  kilogs.  of  bone  black    .    .    .  100  kilogs.  of  potassa  at  50°. 
100       "       raw  animal  matters  100        "  "  " 

We  see,  therefore,  how  variable  are  the  "hard 
facts"  presented  by  practical  men. 

3.  An  English  periodical,  the  London  Journal  of 
Arts,  of  July,  1852,  recommends  from  15  to  20  kilo- 
grammes of  potassa  for  100  kilogrammes  of  animal 
substances.  With  such  a  proportion  of  animal  sub- 
stances, it  will  be  impossible  to  produce  a  fusion,  and 
the  experiments  of  Mr.  Schinz  prove  that  100  kilo- 
grammes of  potassa  will  fuse  at  most  from  130  to 
140  kilogrammes  of  animal  matters. 

If,  in  a  general  way,  and  as  Mr.  Fleck  advises, 
an  average  proportion  of  equal  parts  of  potassa  and 
animal  substances  be  adopted,  we  should  nevertheless 
modify  the  ratio  with  the  nature  of  the  substances 
employed,  as  their  yield  in  nitrogen  is  quite  variable. 

Satisfactory  answers  to  the  important  questions 
here  mentioned  cannot  be  made  except  after  a  great 
many  experiments.    The  analytical  chemist  has  not 


232 


MANUFACTURE  OF  COLORS. 


generally  occasion  to  handle  the  fused  materials,  and 
the  manufacturer  possesses  no  rapid  process  for  deter- 
mining the  composition  of  each  fused  batch,  in  order 
to  be  enabled  to  undertake  a  series  of  experiments 
without  stopping  the  manufacturing  operations,  and 
without  being  obliged  to  arrive  at  the  yield  of  each 
batch  by  a  separate  crystallization. 

The  following  process  gives  results  which  are  more 
than  sufficiently  accurate  for  practical  use.  It  does 
not  require  much  time,  or  a  great  chemical  knowl- 
edge. Moreover,  as  manufacturing  chemists  possess 
no  accurate  way  of  testing  the  ferrocyanides,  this 
method  will  be  of  some  interest  to  them. 

This  method  is  based  upon  the  precipitation  of  the 
ferrocyanide  of  potassium  held  in  an  acid  solution  of 
a  sample  from  the  fused  mass,  by  a  titrated  solution 
of  iron.  There  were  two  difficulties  to  overcome. 
The  first  was  the  determination  of  the  exact  point  of 
saturation,  which  is  not  readily  ascertained  on  account 
of  the  property  possessed  by  Prussian  blue  of  remain- 
ing suspended  for  a  long  time  in  the  liquor.  The  second 
was  the  known  property  of  Prussian  blue,  of  carrying 
down  with  it  a  certain  proportion  of  ferrocyanide  of 
potassium.  The  first  difficulty  was  overcome  by  a  pe- 
culiar mode  of  operation,  which  is  of  general  interest, 
inasmuch  as  it  seems  to  open  a  new  field  in  volumetric 
analysis,  especially  w^ien  there  are  intensely  colored 
precipitates.  A  drop  of  the  liquor,  colored  by  a  pre- 
cipitate, is  deposited  upon  a  piece  of  unsized  paper. 
The  precipitate  remains  where  it  has  touched  the 
paper,  but  the  liquor  spreads  itself  around,  and  forms 
a  colorless  ring,  which,  by  means  of  a  proper  reagent, 
may  be  made  to  assume  a  characteristic  coloration. 
In  our  special  case,  a  blue  color  is  obtained  with 


BLUE  COLORS.  233 


an  iron  solution  before  the  saturation,  and  with  a  so- 
lution of  ferrocyanide  after  saturation. 

The  point  where  the  first  reaction  ceases,  and 
where  the  second  begins,  is  within  the  limits  of  two 
to  four  drops,  and  the  accuracy  of  the  test  is  within 
J  to  I  of  1  per  cent.,  which  is  quite  sufficient  in 
practice. 

The  second  difficulty  is  overcome  by  direct  experi- 
ment, and  two  or  three  tests  agreeing  together  will 
show  that  the  proportion  of  precipitated  ferrocyanide 
of  potassium  is  one-twentieth  of  the  quantity  present. 
The  sulphocyanide  of  potassium  present  in  the  fused 
substances  is  no  impediment  to  the  analysis,  because 
no  sulphocyanide  of  iron  is  formed  until  all  the  ferro- 
cyanide of  potassium  is  precipitated.  We  have  said 
enough  for  experienced  chemists;  however,  we  advise 
the  employment  of  a  moderately  concentrated  solu- 
tion of  a  salt  of  peroxide  of  iron.  The  iron,  held  in 
the  solution  occupying  100  divisions  of  a  graduated 
burette,  is  carefully  determined  after  its  precipitation 
with  ammonia.  The  weight  found  will  be  used  for 
determining  that  of  the  sample  to  be  taken,  in  order 
that  each  division  of  the  burette  be  equal  to  1  per 
cent,  of  ferrocyanide  of  potassium. 

The  formula  is — 

.  2.257 
1  :  2.25t  +  -^Q-  ::  n  :  x, 

in  which  n  is  the  quantity  of  oxide  of  iron  found  in 
100  volumes  of  the  titrated  liquor,  and  x  the  weight 
of  the  raw  fused  mass  to  be  employed  for  the  test. 
As  the  fused  mass  is  very  hygroscopic  and  difficult 
to  grind,  it  is  advisable  to  take  a  certain  weight  of  it, 
and  reduce  by  calculus  the  number  of  divisions  of  the 
titrated  liquor  or  percentage  to  the  weight  x.  For 


234 


MANUFACTTJRE  OF  COLORS. 


instance,  if  8.98  grammes  of  sample  show  12.5  divi- 
sions, or  12.5  per  cent.,  x  grammes  will  give  y  per 
cent. 

Preparation  of  the  titrated  liquor. — A  pure  sul- 
phate of  iron,  without  copper  or  excess  of  base,  is 
prepared  as  follows :  Dissolve  in  boiling  water  250 
grammes  of  sulphate  of  iron,  and  add  a  small  quantity 
of  sulphuric  acid  and  a  few  clean  scraps  of  iron.  Let  it 
stand  until  the  liquor  is  clear  and  of  a  pure  green  color, 
then  filter  it  rapidly,  and  allow  it  to  cool  in  a  covered 
vessel.  After  the  crystals  have  been  dried  in  several 
successive  sheets  of  unsized  paper,  83.28  grammes  of 
them  are  weighed  and  dissolved  in  about  750  grammes 
of  water.  The  solution  is  heated  in  a  porcelain  dish, 
and  nitric  acid  is  added  several  times,  until  red  vapors 
cease  to  be  disengaged.  The  liquor  is  then,  together 
with  the  washings  of  the  dish,  poured  into  a  vessel 
holding  1  litre,  and  v^hen  it  is  cold,  sufficient  pure 
water  is  added  to  make  up  the  capacity  of  a  litre.  100 
cubic  centimetres  of  this  titrated  liquorwill  precipitate 
10  grammes  of  pure  ferrocyanide  of  potassium.  There- 
fore, every  cubic  centimetre  poured  out  will  corre- 
spond to  1  per  cent. 

Analytical  operation. — Different  portions  of  the 
fused  substances  are  ground  together,  and  10  grammes 
w^eighed.  This  is  dissolved  in  warm  water,  the  solu- 
tion is  filtered,  and  the  residue  is  washed  several  times 
with  warm  water.  A  few  drops  of  the  titrated  liquor 
are  then  added,  which  produce  a  brown  and  blue  pre- 
cipitate. To  neutralize  the  free  alkali  of  the  solution, 
hydrochloric  acid  is  then  poured  in,  the  more  slowly 
as  the  brown  precipitate  gradually  disappears,  and  the 
blue  one  becomes  more  apparent.     JS^o  account  is 


BLUE  COLORS. 


235 


taken  of  the  gelatinous  silica  which  is  separated. 
Then  four  or  five  drops  of  the  titrated  liquor  are 
poured  in,  and  a  drop  of  the  blue  liquor  is  deposited 
by  means  of  a  glass  rod  upon  a  piece  of  unsized 
paper.  The  colorless  ring  formed  around  the  blue 
precipitate  is  touched  with  another  rod  wet  with  a 
solution  of  a  salt  of  peroxide  of  iron,  and  if  a  blue 
color  appears,  the  operation  is  continued  as  before. 
"When  the  ring  becomes  brown-red,  from  the  presence 
of  sulphocyanide,  the  test  is  made  with  a  solution  of 
ferrocyanide,  until  a  blue  again  appears.  We  should 
remark:  First,  that  the  coloration  takes  place  only 
after  a  certain  length  of  time;  second,  that  it  appears, 
in  the  majority  of  cases,  in  the  middle  of  the  border, 
and  not  at  the  extreme  edge.  In  order  to  see  how 
accurate  this  test  is,  the  liquor  is  filtered  at  the  end 
of  the  operation,  and  an  addition  of  ferrocyanide  will 
give  a  very  pale  blue  coloration,  if  any. 

The  manufacturer  should  also  note,  before  the  test 
is  made,  the  total  weight  of  the  fused  mass,  which 
weight  may  often  vary  from  unknown  causes. 

6th.  Preparation  of  Prussian  Blue  by  the  Stephens  Process. 

The  invention  comprises  : — 

1.  Several  improvements  in  the  manufacture  of  the 
ferrocyanides  of  potassium  and  sodium. 

2.  A  process  for  rendering  Prussian  blue  soluble, 
and  therefore  better  adapted  for  dyeing,  printing,  and 
writing. 

We  shall  describe  these  two  improvements  succes- 
sively, in  the  order  presented  by  the  inventor. 

Mrst  improvement — This  consists  in  collecting  the 
gaseous  products,  which,  in  the  ordinary  preparation 
of  ferrocyanides  with  animal  substances,  are  lost  in 


236 


MANUFACTURE  OF  COLORS. 


the  air,  and  in  converting  them  into  the  ferrocyanide 
of  sodium  or  of  potassium.  There  is,  therefore,  a 
greater  yield  of  the  ferroeyanides. 

The  apparatuses  necessary  for  these  operations  are 
simple  enough  to  be  explained  in  writing,  without 
having  recourse  to  drawings.  These  apparatuses 
are : — 

1.  An  iron  retort  filled  with  alkali  and  animal 
matters,  or  any  other  substance  holding  nitrogen  and 
producing  ammonia.  This  retort  should  be  brought 
to  a  dark  read  heat.  It  is  provided  with  a  cover, 
which  is  carefully  luted  on  during  the  operation. 

2.  Another  retort  similar  to  the  preceding  one. 

3.  An  hermetically  closed  vessel,  of  a  cylindrical,  or 
any  other  convenient,  shape.  It  is  charged  with  an 
alkali,  and  should  be  maintained  at  a  red  heat  during 
the  whole  operation. 

4.  A  closed  vessel,  holding  an  alkaline  lye,  and 
provided,  for  the  escape  of  gases,  with  a  pipe  similar 
to  a  lamp  burner. 

5.  A  pipe  connecting  the  retort  with  the  cylinder, 
and  delivering  into  the  latter  vessel  the  gases  result- 
ing from  the  carbonization  of  the  animal  substances 
in  the  retort. 

6.  A  tube  delivering  the  gases  from  the  retort  into 
the  vessel  holding  the  caustic  lye.  It  is  already 
understood  that  the  retort  and  the  cylinder  are 
placed  in  furnaces,  the  fire  of  which  is  regulated  by 
appropriate  dampers. 

Everything  being  arranged  in  the  aforesaid  manner, 
the  gases  produced  in  the  carbonizing  retort  pass 
into  the  cylinder  holding  fused  potassa  (or  soda),  and 
form  there  a  certain  quantity  of  ferrocyanide  of  potas- 
sium (or  of  sodium).   The  portion  of  the  gases  which 


BLUE  COLORS. 


237 


has  not  combined  with  the  alkali,  escapes  through  the 
tube  into  the  closed  vessel,  and  there  forms  another 
combination  with  the  alkaline  lye.  Lastly,  the  un- 
combined  gas  escapes  through  the  burner.  The  state 
of  the  operation  is  watched  by  burning  the  gas,  and 
when  the  flame  becomes  small  and  weak,  the  commu- 
nication between  the  retort  and  the  cylinder  is  inter- 
rupted. The  second  retort,  which  has  been  charged 
with  fresh  substances,  is  then  connected  with  the 
cylinder,  and  the  operation  proceeds  as  before. 

"When  the  gaseous  products  of  a  certain  number  of 
charges  have  traversed  the  cylinder  charged  with 
alkali,  it  is  opened,  and  its  contents,  consisting  of 
more  or  less  ferrocyanide  of  potassium  or  of  sodium, 
are  poured  into  a  closed  iron  vessel  where  diey  cool 
off.  They  are  then  lixiviated  with  pure  water,  in  the 
ordinary  way. 

The  decomposition  of  the  carbonized  animal  sub- 
stances may  be  completed  in  the  same  retort,  by 
increasing  the  fire,  and  stirring  the  contents.  During 
that  time,  the  carbonization  goes  on  in  the  other 
retort,  at  a  lower  temperature. 

A  similar  efi'ect,  that  is,  the  absorption  of  the 
gaseous  products,  may  be  obtained  by  placing  in  a 
conical  iron  chimney,  with  a  grate  at  the  bottom,  dry 
potassa  or  soda,  and  passing  the  gases  through  it. 
This  chimney,  with  its  contents,  may  be  removed 
when  the  flame  becomes  weak.  The  alkali  is  used 
for  several  operations,  and  is  then  treated  in  the  ordi- 
nary manner  for  the  extraction  of  the  ferrocyanide  of 
potassium  or  sodium. 

Second  improvement — This  consists  in  submitting 
the  Prussian  blue  to  a  treatment,  by  which  it  becomes 
more  easily  soluble.     The  Prussian  blue  resulting 


238 


MANUrACTUEP:  OF  COLORS. 


from  the  combination  of  ferrocyanide  of  potassium, 
and  of  an  iron  salt,  or  the  ordinary  commercial  article, 
is  put  into  an  earthenware  pot,  and  just  covered  with 
some  concentrated  acid. 

We  may  employ  hydrochloric,  or  sulphuric,  or  any 
other  acid,  having  sufficient  action  upon  the  iron; 
nevertheless,  hydrochloric  acid  is  to  be  preferred.  If, 
however,  sulphuric  acid  be  used,  it  should  be  diluted 
with  an  equal  volume  of  water,  when  the  paste  of  blue 
and  acid  begins  to  turn  white. 

The  Prussian  blue  should  remain  in  the  acid  from 
24  to  48  hours,  or  even  longer.  The  mixture  is  then 
well  stirred  in  a  large  quantity  of  water,  in  order  to 
remove  the  iron  salts.  After  settling,  the  liquid  is 
siphoned  off.  A  new  quantity  of  water  is  then  added, 
and  the  operation  is  continued  until  all  of  the  acid  and 
soluble  iron  salts  are  removed.  When  the  washing  is 
complete,  a  few  drops  of  a  solution. of  ferrocyanide  of 
potassium  produce  no  precipitate  in  the  liquors.  The 
blue  is  then  drained  upon  a  filter. 

The  Prussian  blue,  thus  prepared,  contains  less 
iron  than  the  ordinary  commercial  article.  It  is  this 
modification  which  renders  it  more  easily  soluble. 
The  drained  product  may  be  slowly  dried  in  a  stove 
room. 

After  this  preparation,  the  blue  is  thoroughly  mixed 
with  oxalic  acid,  and  pure  water  is  added  by  small 
portions  at  a  time,  in  quantity  variable  with  the 
greater  or  less  degree  of  concentration  desired.  The 
proportion  of  oxalic  acid  varies  also  with  that  of  the 
water  added. 

It  will  be  ascertained  by  trial  that  Prussian  blue, 
which  has  been  macerated  in  the  aforesaid  manner, 
will  require  for  its  solution  a  much  smaller  propor- 
tion of  oxalic  acid. 


BLUE  COLORS. 


239 


One  part  of  oxalic  acid  will  dissolve  six  parts  of 
Prussian  blue,  weighed  before  maceration  in  hydro- 
chloric or  sulphuric  acid.  These  proportions  are 
suflBcient  for  a  concentrated  solution  ;  but  more  oxalic 
acid  will  be  needed  for  a  more  dilute  solution. 

A  Prussian  blue,  which  has  not  been  macerated  in 
the  strong  acids,  will  require  from  two  to  three  times 
its  weight  of  oxalic  acid,  and  yet,  there  will  be  a  ten- 
dency to  precipitation  in  the  solution. 

The  principal  obstacle  to  the  employment  of  this 
fine  color  for  dyeing,  printing,  and  writing  resulted 
from  its  supposed  insolubility ;  but  the  process  which 
we  have  just  indicated,  and  which  produces  an  en- 
tirely soluble  Prussian  blue,  renders  it  applicable 
to  the  dyeing  and  printing  of  every  cloth  and  sub- 
stance which  may  be  dyed  and  printed. 

The  process  indicated  above  is  not  the  only  one 
known  for  rendering  Prussian  blue  soluble.  An 
aqueous  solution  of  this  color  may  also  be  obtained 
by  precipitating  the  nitrate  or  sulphate  of  sesqui- 
oxide  of  iron,  and  possibly  the  perchloride,  with  a 
great  excess  of  ferrocyanide  of  potassium.  The  pre- 
cipitate is  very  soluble  in  pure  water,  but  insoluble 
in  water  holding  chloride  of  sodium  or  various  other 
salts.  This  property  allows  of  the  separation  of  the 
precipitate. 

7th.  English  Process  for  the  Manufacture  of  Prussian  Blue, 

The  following  process,  usually  employed  in  Eng- 
land, gives  a  Prussian  blue  quite  as  fine  as  that  of 
Berlin,  and  has  a  great  analogy  with  the  method 
actually  practised  in  France. 

Ox  blood,  mixed  with  oxide  of  iron,  is  dried  in  a 
reverberatory  furnace,  the  bed  and  sides  of  which,  to 


240 


MA^^UFACTUKE  OF  COLORS. 


a  height  of  about  twenty  to  twenty-five  centimetres, 
are  formed  of  cast-iron  plates  bolted  together,  an^ 
with  the  joints  made  tight  by  a  clayish  cement. 
During  the  operation,  the  mass  is  continually  stirred 
with  an  iron  bar.  This  furnace  should  have  a  high 
stack  with  a  good  draft,  so  as  to  carry  away  the 
vapors,  which  are  singularl}^  fetid.  "When  the  blood 
is  perfectly  dried,  which  is  a  tedious  process,  it  is 
removed  from  the  furnace  and  broken  into  fragments 
while  it  is  still  hot.  The  division  will  be  more  diffi- 
cult if  the  blood  be  cold.  In  fine  weather,  its  drying 
may  be  completed  in  the  sun.  When  it  is  not  imme- 
diately mixed  with  the  alkali,  the  powdered  blood 
should  be  kept  in  open  vessels  and  in  a  cool  and 
aerated  place,  otherwise  it  will  ferment  and  produce 
a  disagreeable  smell,  and  becoming  viscous,  it  will 
be  difficult  to  mix  with  the  alkali. 

The  "blood  lye"  or  solution  of  crude  ferrocyanide  is 
advantageously  prepared  with  soda,  which  is  cheaper 
than  potassa.  The  proportions  are  one  part  of  dry 
soda  to  six  parts  of  perfectly  dried  blood.  The  soda 
ash  should  be  free  from  sulphides,  and  on  that  ac- 
count it  is  preferable  to  use  the  crystals,  which  are 
completely  dried. 

The  mixture  of  oxide  of  iron,  blood,  and  alkali  is 
calcined  in  a  large  cast-iron  crucible  or  kettle,  which 
is  covered,  without,  however,  entirely  excluding  the 
contact  of  the  air.  This  imperfect  closing  of  the 
vessel  is  for  the  purpose  of  diminishing  the  rapidity 
of  the  combustion. 

The  two  operations  of  calcination,  and  desiccation 
of  the  blood,  are  conducted  simultaneously,  and  with 
^   economy  of  fuel.    The  calcining  vessel  is  placed  on 
the  forepart  of  the  reverberatory  furnace,  near  the 


BLUE  COLORS. 


241 


fire-bridge,  where  the  intensity  of  the  fire  is  greatest. 
The  drying  of  the  blood  takes  place  near  the  chimney. 

The  mixture  to  be  calcined  soon  softens,  takes  fire, 
and  sinks  considerably.  The  cover  of  the  vessel  is 
then  raised  with  a  hook,  and  a  new  portion  of  materials 
is  introduced,  and  so  on,  until  the  vessel  is  filled. 
After  ten  hours  of  calcination,  the  vapors  cease  to 
catch  fire,  and  the  animal  substances  are  entirely 
charred.  The  temperature  is  then  raised,  so  as  to 
redden  the  metallic  vessel.  The  alkaline  charcoal 
enters  into  a  sort  of  fusion,  and  sticks  to  the  spatula 
with  which  it  is  stirred.  After  one  hour  more  of  red 
heat,  the  contents  are  removed  with  an  iron  ladle,  and 
thrown  into  an  iron  vessel,  which  holds  a  volume  of 
cold  water  about  double  that  of  the  blood  used. 
After  boiling,  the  liquor  is  filtered  through  several 
thicknesses  of  cloth,  and  the  residue  is  again  boiled 
and  filtered. 

All  of  the  liquors  and  washings  are  collected  in 
large  but  shallow  cisterns,  and  exposed  to  the  air. 
They  are  stirred  now  and  then,  in  order  to  decompose 
the  sulphides.  When  the  lye  no  longer  gives  a  black 
precipitate  with  the  acetate  of  lead,  it  is  treated  with 
two  parts  of  alum,  and  one-half  part  of  sulphate  of 
iron,  for  each  part  of  dry  carbonate  of  soda  employed. 
The  sulphate  of  iron  has  been  previously  oxidized  by 
its  ebullition  with  a  very  small  proportion  of  nitric 
acid,  or  by  passing  some  chlorine  through  it.  The 
same  result  may  be  obtained  by  calcining  it  in  the 
air,  at  a  very  low^  temperature.  The  alum  and 
sulphate  of  iron  are  dissolved  only  when  they  are 
going  to  be  used.  The  mixture  of  the  liquors  is 
effected  by  pouring  the  solution  of  the  sulphates  into 
that  of  ferrocyanide,  and  stirring  continually.  The 
16 


242 


MANUFACTURE  OF  COLORS. 


precipitate  of  Prussian  blue  is  washed  several  times 
by  decantation  with  pure  water.  The  washing  should 
be  continued  as  long  as  the  liquor  precipitates  by  the 
addition  of  ammonia.  The  blue  is  collected  upon 
cloths,  which  are  folded  and  pressed  when  it  has 
acquired  a  certain  consistency.  The  drying  is  effected 
in  the  shade  and  in  stove-rooms,  the  temperature  of 
which  latter  should  not  be  over  25°  C. 

"When  the  blue  is  sold  in  paste  for  distemper  paint- 
ing, and  the  printing  of  paper  hangings,  it  is  evident 
that  it  ought  not  to  be  pressed. 

As  long  as  Prussian  blue  is  pasty  and  wet,  it  pre- 
serves its  pure  color.  But  it  seldom  happens  even 
after  the  best  conducted  drying  in  a  well  ventilated 
room,  that  the  blue  fails  to  acquire  a  slightly  green 
tinge,  which  defect  is  not  seen  in  the  fine  Berlin 
blues.  This  defect  is  attributed  to  the  production  of 
a  small  quantity  of  ammonia,  resulting  from  the 
decomposition  of  prussic  acid. 

The  addition  of  a  certain  proportion  of  acid  sulphate 
of  potassa  preserves  the  fine  color  of  the  Prussian 
blue,  and  admits  of  its  employment  with  vegetable 
and  essential  oils.  This  salt  results  from  the  decom- 
position of  nitrate  of  potassa  by  sulphuric  acid,  and 
is  cheap,  and  easily  found  in  the  trade.  It  is  probable 
that  the  acid  sulphate  of  soda  would  have  the  same 
effect. 

The  expense  of  manufacture  may  be  diminished 
by  substituting  for  the  alum  a  sulphate  of  alumina, 
which  may  be  prepared  on  the  spot,  and  does  not 
require  to  be  free  from  iron.  This  sulphate  of  alumina 
is  prepared  by  making  a  stiff  paste  of  clay  and  sul- 
phuric acid,  and  moulding  it  into  bricks,  which  are 
heated  in  a  little  space  left  at  the  end  of  the  blood 


BLUE  COLORS. 


243 


drying  furnace.  The  liquor  resulting  from  the  lixi- 
viation  of  these  bricks  is  employed,  directly  and  with- 
out evaporation,  with  the  sulphate  of  iron  and  the 
solution  of  crude  ferrocyanide. 

An  important  condition,  in  the  manufacture  of 
Prussian  blue,  is  to  effect  the  calcination  at  the  proper 
temperature.  An  excess  of  heat  is  injurious  to  the 
yield.  In  general,  it  is  better  to  calcine  longer  and 
at  a  lower  temperature. 

A  few  manufacturers  employ  the  crystallized  ferro- 
cyanide of  potassium,  with  which  they  obtain  the 
Prussian  blue  directly,  and  without  the  addition  of 
acid.  But  it  is  easy  to  see  that  this  process  is  not 
economical.  The  crystallized  prussiate  is  obtained 
after  saturation  of  the  excess  of  alkali  in  the  crude 
"blood  lye."  Subsequently,  when  mixing  alumina 
with  the  Prussian  blue,  which  contributes  to  its  beauty 
and  its  velvety  appearance,  another  alkali  is  employed 
for  precipitating  the  alumina  from  the  alum.  There 
results  therefore  a  double  employment  of  chemicals, 
whereas,  in  the  ordinary  process,  the  excess  of  alkali 
in  the  raw  solution  of  ferrocyanide  decomposes  the 
alum. 

A  manufacturer  of  Glasgow  proposed  to  use  the 
bone  black  which  had  been  used  for  clarifying  the 
sugar  of  refineries.  This  black,  which  was  used  only 
as  manure,  is  again  calcined  with  one-thirtieth  part 
of  alkali.  The  result  is  an  abundant  production  of 
alkaline  prussiate,  without  those  disagreeable  smells 
produced  by  blood  and  other  uncalcined  animal  sub- 
stances. The  most  interesting  part  of  the  process  is, 
that  the  residue  left  after  the  lixiviation  of  the 
cyanides  is  a  very  energetic  discolorizing  substance, 
which  is  sold  again  to  the  sugar  refiner.    It  appears 


244 


MANUFACTURE  OF  COLORS. 


that  the  same  material  may  be  used  several  times 
successively  for  clarifying  sugars  and  producing 
cyanides. 

§  2.  Paris  Hue, 

Paris  blue,  also  called  TurnhulVs  Hue,  is  a  very 
handsome  dark  violet-blue  pigment,  in  which  the 
projDortions  of  protocyanide  and  sesquicyanide  do  not 
appear  to  be  in  the  same  ratio  as'  in  the  ordinary 
Prussian  blue.  It  is  said  that  its  chemical  formula 
is  represented  by  3  equivalents  of  protocyanide  and 
1  of  sesquicyanide  of  iron. 

Paris  blue  is  prepared  by  different  processes,  the 
products  of  which  are  not  always  uniform  in  tone  and 
in  intensity  of  coloration.  Generally,  a  green  and 
pure  protosulphate  of  iron  is  precipitated  by  the  red 
prussiate  of  potash  (ferri cyanide  of  potassium),  and 
the  mode  of  operation  is  the  same  as  with  the  ordi- 
nary Prussian  blue. 

The  sulphate  of  iron  may  also  be  precipitated  by  a 
solution  of  raw  ferrocvanide,  and  the  excess  of  alkali 
removed  by  washings  with  pure  water.  The  precipi- 
tate is  then  treated  by  hypochlorite  of  lime  (bleach- 
ing powder)  dissolved  in  cold  water,  and  lastly, 
washed  with  dilute  hydi'ochloric  acid,  and  rinsed  in 
pure  water. 

Paris  blue  is  also  produced  by  dissolving  separately 
in  15  parts  of  water,  6  parts  of  sulphate  of  protoxide 
or  of  peroxide  of  iron,  and  six  parts  of  yellow  prussiate 
of  potassa.  The  two  liquors  are  mixed,  and  there  are 
added  to  them  one  part  of  sulphuric  acid,  and  twenty- 
four  parts  of  concentrated  hydrochloric  acid.  The 
whole  is  stirred,  and,  after  standing  a  few  hours,  is 
treated  by  a  filtered  solution  of  hypochlorite  of  lime 


/ 


BLUE  COLORS. 


245 


(bleaching  powder)  dissolved  in  eighty  parts  of  water. 
This  latter  solution  is  poured  by  small  quantities  at 
a  time,  and  stopped  when  there  is  an  effervescence  due 
to  the  disengagement  of  chlorine.  The  precipitate  is 
then  allowed  to  settle,  and  it  is  afterwards  washed 
several  times  with  pure  water  by  decantation.  After 
draining,  it  is  moderately  heated  with  dilute  nitric 
acid,  until  it  has  acquired  a  fine  dark  blue  color. 

According  to  Mr.  Raymond,  a  handsome  quality  of 
Paris  blue  is  obtained  by  precipitating  a  nitrate  of 
sesquioxide  of  iron  with  the  yellow  prussiate  (ferro- 
cyanide  of  potassium)  or  with  "blood  lye." 

Mr.  R.  Warington,  who  has  carefully  studied  the 
Turnbull  blue,  states  that  several  efficient  reagents 
may  be  employed  in  its  preparation,  that  is,  1,  the 
bichromate  of  potassa ;  2,  the  chlorate  of  potassa ;  3, 
a  soluble  persalt  of  iron ;  4,  a  solution  of  hypochlorite 
of  lime. 

"  When  bichromate  of  potassa  is  used,  only  one- 
third  of  one  equivalent  should  be  taken,  because  this 
salt  gives  three  equivalents  of  available  oxygen.  One 
equivalent  of  chlorate  of  potassa  is  sufficient  for  the 
oxidization,  and  sufficient  hydrochloric  acid  should 
be  added  for  decomposing  the  salt  and  setting  its 
acid  at  liberty.  Hypochlorite  of  lime  (bleaching 
powder)  is  open  to  the  objection  of  producing  a  quan- 
tity of  sulphate  of  lime,  when  sulphate  of  iron  or 
sulphuric  acid  is  used.  In  the  third  case,  when  a 
persalt  of  iron  is  the  oxidizing  agent,  the  sulphate  of 
peroxide  is  to  be  preferred.  One  equivalent  of  it  is 
necessary  for  one  equivalent  of  oxygen,  and  there  is 
produced  enough  sulphuric  acid  to  combine  with  the 
oxidized  potassium  after  the  iron  has  been  reduced  to 
the  protoxide  state. 


246 


MANUFACTURE  OF  COLORS. 


"  In  the  preparation  of  the  sulphate  of  peroxide  of 
iron,  bichromate  of  potassa  or  chlorate  of  potassa  is 
more  advantageous  than  nitric  acid,  and  there  should 
be  a  sufficient  proportion  of  sulphuric  acid  to  dissolve 
the  oxide  of  chromium  produced.  The  decomposition 
of  the  chlorate  of  potassa  should  always  be  effected 
with  hydrochloric  acid.  Since  the  protosulphate  of 
iron  absorbs  one-half  of  one  equivalent  of  oxygen  to 
become  sesquisulphate,  it  is  evident  that  one-sixth 
of  one  equivalent  of  bichromate  of  potassa,  or  one- 
tenth  of  one  equivalent  of  chlorate  of  potassa  with 
the  required  proportion  of  acid,  is  sufficient  for  the 
transformation.  When  the  oxidizing  solution  is  pre- 
pared with  the  chlorate  of  potassa,  this  solution,  after 
the  oxidization  of  the  white  Prussian  blue,  may  be 
precipitated  by  ferrocyanide  of  potassium  for  a  new 
operation.  If  the  bichromate  of  potassa  be  used,  the 
protoxide  of  chromium  will  be  precipitated  to  a  cer- 
tain extent  by  the  ferrocyanide  of  potassium,  and  will 
contribute  to  the  brightness  of  the  color." 

Mr.  G.  C.  Habich,  a  chemist  who  has  paid  great 
attention  to  the  manufacture  of  Paris  blue,  has  pro- 
posed several  valuable  improvements,  which  render 
its  preparation  more  certain  and  more  economical. 

"  Among  those  coloring  materials,"  says  he,  "which, 
from  their  numerous  uses,  require  to  be  manufactured 
on  a  large  scale,  Prussian  blue  is  certainly  foremost. 

"  Its  great  qualities  of  body,  and  intensity  of  colora- 
tion, will  always  insure  it  a  large  sale ;  moreover,  its 
mixture  with  chrome  yellow  produces  a  fine  green 
cinnabar  or  leaf  green  {Laubgrun), 

"The  methods  followed  in  certain  works  for  the 
manufacture  of  this  product,  appear  to  me  too  ex- 
pensive.   Thus  many  persons  still  prefer  the  process 


BLUE  COLORS. 


247 


by  which  the  white  precipitate,  resulting  from  the 
decomposition  of  ferrocyanide  of  potassium  by  sul- 
phate of  iron,  is  rendered  blue  by  means  of  sulphuric 
and  nitric  acids,  although  it  is  impossible  to  obtain 
with  this  product  a  good  commercial  green. 

"  I  shall  explain  several  processes  by  which  the 
preparation  of  this  product  will  be  certain  and 
economical. 

''First  Process. — This  process  is  based  upon  the 
treatment  of  the  white  precipitate  by  the  chlorine 
held  in  aqua  regia. 

''The  precipitate  of  ferrocyanide  of  potassium 
(yellow  prussiate)  by  the  sulphate  of  protoxide  of 
iron,  is  prepared  in  the  ordinary  manner ;  but  the 
sulphate  employed  should  be,  as  far  as  possible,  free 
from  oxide  (basic  sulphate).  This  result  is  arrived 
at  by  keeping  in  the  acid  solution  of  sulphate  of  iron, 
a  small  quantity  of  metallic  iron,  which,  at  the  same 
time,  precipitates  the  copper  which  may  be  present. 
Besides,  it  is  desirable  to  operate  the  precipitation 
in  the  hot  blood  lye  (crude  prussiate  of  potassa),  in 
order  to  avoid  an  absorption  of  oxygen,  and  a  prema- 
ture change  of  the  precipitate  to  a  blue  color.  Only 
the  blue  produced  by  the  action  of  chlorine,  nitric 
acid,  etc.,  upon  the  white  precipitate,  possesses  the 
intensity  required  in  this  pigment.  That  resulting 
from  the  oxidization  by  the  air,  even  after  all  the 
hydrate  of  oxide  of  iron  has  been  removed  by  hydro- 
chloric acid,  never  produces  a  fine  color,  especially 
for  the  preparation  of  greens. 

"  In  regard  to  the  proportion  of  sulphate  of  iron, 
the  general  mistake  is  in  employing  too  little  of  it. 
"When  ninety  kilogrammes  of  sulphate  of  iron  have 
been  added  to  one  hundred  kilogrammes  of  ferro- 


248 


MANUFACTURE  OF  COLORS. 


cyanide  of  potassium,  a  drop  of  iron  solution  in  the 
filtered  liquor  produces  no  precipitate.  However,  the 
white  precipitate  has  carried  with  it  a  certain  propor- 
tion of  ferrocyanide,  which  maybe  removed  by  wash- 
ing. This  proportion  of  a  costly  chemical  is  there- 
fore lost,  and  in  order  to  avoid  its  waste,  we  propose 
the  following  mode  of  operation.  The  iron  solution 
is  poured  into  that  of  ferrocyanide,  which  is  stirred 
all  the  time,  until  precipitation  no  longer  takes  place, 
then  one  volume  of  the  same  iron  solution,  equal  to 
one-ninth  of  that  already  poured  in,  is  added.  If  we 
continue  the  stirring  for  about  fifteen  minutes,  we 
maybe  sure  that  the  whole  of  the  ferrocyanide  carried 
down  by  the  precipitate  is  decomposed.  We  have, 
therefore,  reached  the  degree  of  economy  which  may 
be  expected  at  this  period  of  the  manufacture. 

"  The  precipitate  which  has  been  left  to  drain  until  it 
has  become  a  thick  magma,  is  then  peroxidized  (blued) 
with  a  mixture  of  nitric  and  hydrochloric  acids, 
prepared  several  days  beforehand.  The  proportions 
naturally  depend  upon  the  degree  of  concentration  of 
these  acids,  which  is  ascertained  by  means  of  a  good 
hydrometer,  and  of  corresponding  tables  found  in 
treatises  on  chemistry.  The  mixture  is  so  made  that 
there  are  in  weight  54  parts  of  anhydrous  nitric  acid 
and  36.5  parts  of  anhydrous  hydrochloric  acid.  The 
proportion  of  aqua  regia  necessary  for  turning  to  blue 
the  white  precipitate,  is  10.7  parts  of  anhydrous  nitric 
acid  (in  the  mixture)  for  100  parts  of  ferrocyanide  of 
potassium  employed  for  the  precipitation.  Let  us 
suppose  that  the  nitric  acid  marks  30°  Be.  (sp. 
gr.  =  1.256  according  to  Graham),  and  the  hydro- 
chloric acid  23°  Be.  (sp.  gr.  =  1.185)  ;  the  first  of 
these  acids,  according  to  the  tables  of  Dr.  Ure,  con- 


BLUE  COLORS. 


249 


tains  35.4  per  cent,  of  anhydrous  nitric  acid,  and  the 
second  37.25  per  cent,  of  anhydrous  hydrochloric  acid. 
From  the  preceding  data,  the  aqua  regia  mixture  will 
be  100  kilogrammes  of  the  commercial  nitric  acid 
(holding  35.4  kilogrammes  of  anhydrous  acid),  and 
62.2  kilogrammes  of  the  commercial  hydrochloric 
acid  (holding  23.9  kilogrammes  of  anhydrous  acid). 
Lastly,  40  kilogrammes  of  this  mixture  will  be  suffi- 
cient for  bluing  the  precipitate  resulting  from  100 
kilogrammes  of  ferrocyanide  of  potassium. 

"  The  aqua  regia  is  added  by  small  portions  at  a 
time  to  the  white  precipitate,  which  is  placed  in  a 
wooden  tub,  and  is  stirred  all  the  while.  It  now 
remains  to  ascertain  whether  too  much  acid  has  been 
added,  or  if  the  intensity  of  the  color  may  still  be 
raised  by  a  fresh  addition  of  acid.  Such  defects  may 
result  from  an  improper  preparation  of  the  aqua  regia. 

"  A  small  quantity  of  the  blue  color  is  put  into  a 
glass,  and  a  drop  of  aqua  regia  is  mixed  with  it.  Then 
a  blue  mark  is  made  with  that  sample  of  color  upon 
a  piece  of  paper,  and  is  compared  with  a  similar  mark 
made  with  the  stuff  in  the  tub.  If  this  addition  of 
acid  has  increased  the  intensity  of  the  blue,  too  little 
aqua  regia  has  been  employed,  and  more  should  be 
poured  in.  On  the  other  hand,  if  the  test  sample  has 
become  slightly  greenish,  the  proportion  of  the  acids 
has  been  sufficient  or  too  considerable.  In  order  to 
decide  this  point,  a  new  sample  from  the  tub  is  put 
into  a  test  glass,  and  a  very  small  quantity  of  white 
precipitate  is  added  to  it.  Should  the  color  become 
more  intense,  we  have  the  proof  that  too  much  acid 
has  been  added.  This  defect  is  remedied  by  adding 
by  degrees  a  certain  proportion  of  the  white  pre- 
cipitate, of  which  there  should  always  be  a  certain 


250 


MANUFACTURE  OF  COLORS. 


stock  on  hand,  which  is  preserved  in  well-closed  glass 
or  stoneware  jars. 

"  The  washings  and  the  other  operations  are  then 
effected  in  the  ordinary  manner. 

"Second  Process, — The  white  precipitate  of  ferro- 
cyanide  of  potassium  by  sulphate  of  iron,  is  rendered 
blue  by  a  solution  of  perchloride  of  iron,  which  is 
reduced  to  the  state  of  protochloride  and  may  be  used 
for  another  precipitation,  instead  of  sulphate  of  iron. 

"  This  perchloride  of  iron  is  made  with  iron  ore, 
free  from  clay  and  carbonate  of  lime,  and  which  may 
be  brown  or  red  hematite.  If  such  an  ore  cannot  be 
had,  then  the  residue  of  the  manufacture  of  sulphate 
of  iron,  known  under  the  names  of  caput  mortuum, 
colcotar  and  English  rouge,  may  be  employed.  The 
oxide  of  iron,  w^hatever  its  origin,  is  finely  ground, 
and  then  treated  in  a  lead  tank  with  the  crude  hydro- 
chloric acid  of  the  soda  works,  which  generally  con- 
tains a  certain  proportion  of  iron.  The  mixture  is 
frequently  stirred  for  several  days,  and  when  the 
liquor  is  saturated  with  iron,  it  is  decanted  into 
another  vessel,  where  it  becomes  entirely  clear.  It  is 
this  solution  of  perchloride  of  iron,  which  is  used  for 
bluing. 

"  The  white  precipitate  is  prepared  in  the  manner 
already  described,  and  drained.  The  magma  is 
rapidly  heated  to  the  boiling  point  in  a  copper  vessel, 
and  then  poured  into  a  tub  and  stirred  with  the  solu- 
tion of  perchloride  of  iron,  which  is  admitted  until 
the  color  has  acquired  its  greatest  intensity.  In  this 
operation,  it  is  not  necessary  to  watch  the  bluing 
with  the  same  attention  as  when  the  aqua  regia  is 
used,  because  an  excess  of  perchloride  does  not  alter 
the  purity  of  the  color.    This  perchloride  of  iron  is 


BLUE  COLORS. 


251 


therefore  added  to  a  slight  excess,  that  is,  until  a 
filtered  sample  of  the  liquor  is  turned  decidedly  blue 
by  a  few  drops  of  a  solution  of  ferrocyanide  of  potas- 
sium. When  this  point  is  reached,  the  liquor  is  filtered 
out  (if  it  be  desired  to  save  nearly  all  of  it),  or  the 
precipitate  is  left  to  settle,  and  the  clear  portion  is 
decanted. 

"This  liquor,  as  we  have  said,  is  a  solution  mostly 
of  protochloride  of  iron.  It  is  poured  upon  old  scrap 
iron,  and  may  be  used  instead  of  sulphate  of  iron  for 
a  precipitation  with  ferrocyanide  of  potassium.  This 
saving  is  one  advantage  of  this  method. 

"  The  color  is  washed,  etc.,  in  the  ordinary  manner. 

''Third  Process. — In  this  method,  the  white  precip- 
itate is  rendered  blue  b}^  a  solution  of  perchloride  of 
manganese.  The  economy  of  the  process  depends  on 
local  circumstances,  and  on  this  account,  it  is  neces- 
sary to  state  that  the  price  of  manganese  ore  is  based 
upon  its  yield  in  binoxide,  and  that  the  less  oxidized 
ores  generally  mixed  with  it  may  be  dissolved  in 
cold  hydrochloric  acid.  Therefore,  by  treating  an 
ordinary  ore  by  hydrochloric  acid,  the  value  of  the 
ore  becomes  enhanced,  and  there  is  obtained  at  the 
same  time  a  very  good  reagent  for  bluing  the  white 
precipitate. 

"The  mode  of  operation  is  exactly  the  same  as 
with  the  perchloride  of  iron.  As  the  solution  of  pro- 
tochloride of  manganese,  resulting  from  the  bluing 
treatment,  is  without  particular  value  to  the  manu- 
facturer, we  should  avoid  adding  an  excess  of  per- 
chloride. Therefore,  samples  of  blue  are  frequently 
taken,  and  their  intensity  compared.  This  is  the  only 
test  practicable,  by  reason  of  the  easy  decomposi- 


252 


MANUFACTURE  OF  COLORS. 


tion  of  the  perchloride  of  manganese.  The  remaining 
manipulations  are  as  usual. 

u  fji|^g  residues  of  the  manganese  ores,  after  their 
treatment  by  hydrochloric  acid,  are  carefully  washed 
and  dried  before  being  sold  as  peroxide  or  purified 
manganese. 

''Fourth  Process. — A  solution  of  chromic  acid  is 
also  an  excellent  reagent  for  bluing  the  white  pre- 
cipitate of  ferrocyanide  of  potassium  by  sulphate  of 
iron.  The  only  disadvantage  of  the  method  is,  that 
the  resulting  salt  of  oxide  of  chromium  is  difficult 
to  place  on  the  market. 

"  The  following  is  the  mode  of  operation  :  10  parts 
of  bichromate  of  potassa  are  dissolved  in  100  parts  of 
hot  water,  and  when  the  solution  is  cold,  13.5  parts 
of  concentrated  sulphuric  acid  are  added  to  it.  The 
mixture  is  kept  in  closed  glass  vessels. 

"  The  white  precipitate,  prepared  as  usual,  and  in 
the  form  of  a  magma,  is  heated  to  the  boiling  point. 
The  chromic  liquor  is  then  added,  until  the  maximum 
of  intensity  in  the  liquor  is  reached. 

"  Before  closing  these  remarks  on  Prussian  blue,  I 
shall  again  point  out  the  mistake  made  by  certain 
manufacturers  who  prepare  the  blue  with  the  inten- 
tion of  producing  greens  by  an  admixture  of  chrome 
yellow,  and  who  believe  that  their  mode  of  operation 
is  perfect,  whereas  it  is  wrong.  I  am  acquainted 
with  manufacturers  who  neglect  all  the  precautions 
we  have  mentioned,  and  who  allow  the  white  precipi- 
tate of  ferrocyanide  of  potassium  by  sulphate  of  iron 
to  become  blue  by  the  contact  of  atmospheric  air. 
They  certainly  ignore  the  fact,  that  by  their  process 
they  lose  a  notable  proportion  of  the  ferrocyanide, 
which  is  the  most  expensive  material  of  the  manu- 


BLUE  COLORS. 


253 


factiire.  It  has  been  established  by  accurate  chemical 
experiments,  that  50  per  cent.*^  of  the  ferrocyanide 
employed  in  the  precipitation  of  a  salt  of  protoxide 
of  iron,  is  carried  down  with  the  white  precipitate, 
and  that  during  the  bluing,  the  greater  part  of  this 
ferrocyanide  is  dissolved  and  washed  away.  This 
loss  is  prevented  or  greatly  diminished  when  one  of 
the  above  processes  is  followed  in  bluing.  When  it 
is  desired  to  avoid  ony  waste,  the  liquor  decanted  or 
filtered  from  the  white  precipitate  should  be  collected 
in  a  special  tank,  and  precipitated  by  a  solution  of 
sulphate  of  iron." 

§  3.  Monthiers'^  hlue, 

Mr.  Monthiers  has  discovered  that  Prussian  blue 
will  combine  with  ammonia,  and  that  the  resulting 
color  is  finer  and  more  durable  than  the  ordinary 
article.    The  mode  of  operation  is  as  follows : — 

Pure  hydrochloric  acid  is  saturated  with  iron,  and 
the  resulting  solution  of  protochloride  of  iron  is  mixed 
with  an  excess  of  aqua  ammonia.  The  liquor  is  fil- 
tered, and  the  filtrate  is  received  in  a  solution  of 
ferrocyanide  of  potassium.  The  resulting  white  pre- 
cipitate is  collected  upon  a  filter,  and  left  exposed  to 
the  contact  of  the  air,  when  it  soon  becomes  blue. 
It  is  then  washed  with  a  solution  of  tartrate  of 
ammonia,  in  which  it  is  not  soluble  like  the  ordinary 
blue,  in  order  to  dissolve  any  excess  of  oxide  of  iron 
held  in  it.  The  washing  is  continued  until  nothing 
more  is  dissolved,  when  the  article  is  dried  at  a  low 
temperature. 


*  More  likely  5  per  cent.    See  p.  233. — Trans. 


254 


MANUFACTURE  OF  COLORS. 


§  4.  Testing  the  value  of  Prussian  hlue,  and  its 
adulterations. 

There  are  in  the  market,  under  different  names, 
many  coloring  substances  having  Prussian  blue  for 
a  basis,  and  which  often  contain  quite  a  large  pro- 
portion of  some  white  substance.  The  common  sorts 
of  greens  for  house  painting  are  mixtures  of  Prussian 
blue,  chrome  yellow,  or  some  other  organic  yellow, 
with  a  greater  or  less  proportion  of  white  material. 
As  Prussian  blue  may  easily  be  transformed  into 
ferrocyanide  of  potassium,  Mr.  Brunnquell  thinks 
that  the  method  which  has  already  been  explained 
for  testing  the  crude  ferrocyanide,  may  be  applied  to 
the  analysis  of  Prussian  blue  and  its  mixtures. 

The  operation  is  as  follows  :  Boil  6.79  grammes  of 
the  color  to  be  tested  with  a  solution  of  caustic 
potassa  until  all  the  blue  or  green  coloration  has  dis- 
appeared ;  then  filter,  and  wash  the  residue  several 
times  with  hot  water.  The  liquors  are  tested  as  has 
already  been  explained.  In  this  case,  as  there  is  no 
sulphocyanide  of  potassium,  the  test  is  continued 
until  there  is  no  longer  a  blue  coloration  with  the 
ferric  solution.  At  this  period  of  the  operation  the 
volume  of  this  solution,  which  has  been  poured  out, 
is  noted,  and  a  few  more  drops  added,  until  the  blue 
coloration  reappears  with  a  solution  of  ferrocyanide. 
One-half  of  the  number  of  these  drops  is  added  to  the 
volume  previously  noted,  and  the  percentage  of  Prus- 
sian blue  is  obtained  as  accurately  as  may  be  done  by 
a  volumetric  test.  If  the  blue  precipitate  does  not 
deposit  well  upon  the  paper,  but  runs  towards  the 
edges,  some  common  salt,  or  other  indifferent  salt,  is 
added  to  the  tested  solution.    There  is  a  Prussian 


BLUE  COLORS. 


255 


blue  which  is  soluble  in  pure  water,  but  not  in  a 
solution  of  common  salt. 

There  are  several  ways  of  testing  the  commercial 
white  cyanide  of  potassium.  Baron  Liebig  has  given 
a  process  which  seems  as  accurate  as  possible. 
Messrs.  Fordos  and  Gelis  have  also  published  a 
method  which  does  not  appear  so  accurate,  and  which 
requires  the  employment  of  iodine,  an  expensive  sub- 
stance. As  practical  manufacturers  are  generally 
opposed  to  the  preparation  of  test  liquors,  which  re- 
quire a  certain  degree  of  skill  in  manipulation,  Mr. 
Brunnquell  refers  again  to  his  method  in  case  it  be 
desired  to  avoid  the  expense  necessitated  by  the  Lie- 
big  process.   The  mode  of  operation  is  as  follows : — 

Dissolve  9.246  grammes  of  cyanide  of  potassium  in 
a  small  quantity  .of  water,  and  add  about  the  same 
quantity  of  the  solution  of  pure  sulphate  of  iron. 
The  whole  is  boiled  for  some  time  with  a  solution  of 
potassa,  and  then  filtered,  and  the  residue  washed. 
The  liquors  are  treated  in  the  manner  explained  in 
§  1  and  §  2.  Each  degree  (volume)  of  the  titrated 
liquor  corresponds  to  1  per  cent,  of  pure  cyanide  of 
potassium. 

The  substances  generally  employed  for  adulterating 
Prussian  blue  are :  Alum,  an  excess  of  oxide  of  iron, 
starch,  the  carbonate  and  the  sulphate  of  lime, 
alumina,  and  sulphate  of  baryta. 

The  alum,  oxide  of  iron,  and  alumina  are  dissolved 
by  digesting  the  blue  in  sulphuric  acid,  diluted  with 
eight  to  ten  times  its  weight  of  water.  After  filtering, 
an  excess  of  ammonia  is  added  to  the  liquor,  and 
there  is  produced  an  abundant  reddish  precipitate  of 
alumina  and  oxide  of  iron.    Caustic  potassa  will  dis- 


256 


MANUFACTURE  OF  COLORS. 


solve  the  alumina ;  the  blue  remains  undissolved  in 
the  acid. 

Starch  is  recognized  by  the  eye,  with  or  without 
the  aid  of  a  microscope.  But  the  best  test  consists  in 
boiling  the  Prussian  blue  in  water,  and  filtering  it.  A 
drop  of  iodine  solution  in  the  cold  filtrate  produces 
with  starch  an  intense  blue  coloration. 

Each  time  that  a  Prussian  blue,  stirred  in  pure 
water,  efiervesces  by  the  addition  of  an  acid,  it  is  a 
proof  that  it  is  mixed  with  a  carbonate,  and  if  the 
filtered  liquor,  rendered  neutral,  gives  a  white  pre- 
cipitate with  oxalate  of  ammonia,  carbonate  of  lime 
is  the  adulterant. 

Plaster  of  Paris  (sulphate  of  lime)  is  detected  by 
boiling  the  sample  of  Prussian  blue  in  water  slightly 
acidulated  with  nitric  acid.  The  liquor  is  filtered, 
and  the  blue  remains  upon  the  filter.  A  few  drops  of 
a  solution  of  chloride  of  barium,  added  to  the  filtrate, 
will  produce  a  white  precipitate  of  sulphate  of  baryta. 

We  have  already  seen  that  Prussian  blue  is  ren- 
dered soluble  after  a  treatment  with  hydrochloric 
and  oxalic  acids;  therefore,  if,  after  a  sample  has 
been  rendered  soluble,  there  remains  upon  the  filter 
a  white  substance,  insoluble  in  water  and  acids,  we 
conclude  that  this  blue  has  been  adulterated  with 
sulphate  of  baryta. 

§  5.  Mineral  hlue^  Antiuerjp  hlue. 

Mineral  or  Antwerp  blue  is  a  mixture,  in  variable 
proportions,  of  Prussian  blue,  alumina,  magnesia,  and 
oxide  of  zinc.  Its  color  varies  from  a  light  to  a  dark 
blue,  and  it  is  employed  for  oil  and  distemper  paint- 
ing, and  especially  for  paper  hangings. 

It  is  prepared  like  Prussian  blue,  with  this  differ- 


BLUE  COLORS. 


257 


ence,  that  the  sulphates  of  magnesia  and  zinc,  and  the 
alum,  are  added  to  the  lye  of  crude  ferrocyanide  of 
potassium.  The  remainder  of  the  operation  is  as 
usual. 

The  name  of  "mineral  blue"  is  sometimes  given  to 
white  earths  (kaolins,  etc.),  colored  with  indigo  and 
hydrated  oxide  of  copper.  A  small  quantity  of  Nord- 
hausen  sulphuric  acid  decomposes  Prussian  blue,  and 
dissolves  indigo  without  changing  its  color.  A  few 
drops  of  ammonia,  poured  into  the  liquor,  will  pro- 
duce an  intense  blue  coloration  if  copper  be  present. 

§  6.  Thenard  hlue^  or  cobalt  blue  {subphosphate  of 
cobalt). 

The  discovery  of  this  fine  color  is  due  to  the  chem- 
ist Thenard.  This  blue  is  a  basic  phosphate,  of 
cobalt,  which,  being  calcined  with  alumina,  gives  a 
pigment  sufficiently  handsome  to  replace  ultramarine 
blue,  which  is  more  expensive.  Cobalt  blue  could  be 
advantageously  substituted  for  ultramarine,  even  for 
delicate  paintings,  except  for  one  single  defect, 
pointed  out  by  Mr.  Bourgeois,  it  has  a  violet  hue 
under  artificial  light,  and  this  naturally  defeats  the 
colored  combinations  of  the  artist. 

Cobalt  blue  acquires  all  its  intensity  of  coloration 
only  after  exposure  to  the  air.  Messrs.  Bourgeois  and 
Colomb  have  succeeded  in  giving  it  sufficient  body ; 
and,  although  not  so  pure  in  color  as  ultramarine,  it 
produces,  with  silver  white,  different  tones.  It  should 
always  be  remembered  that  the  tones  produced  with 
cobalt  blue  will  become  more  intense  after  a  lono^ 
exposure  to  the  air,  and  that  they  acquire  a  slightly 
greenish  tinge,  which  is  not  the  case  with  ultra- 
marine. 

17 


258 


MANUFACTURE  OF  COLORS. 


The  preparation  of  cobalt  blue,  according  to  The- 
nard,  is  as  follows :  The  roasted  cobalt  ore  from 
Tunaberg,  Sweden,  is  heated  with  an  excess  of  dilute 
nitric  acid,  and  the  solution  is  evaporated  nearly  to 
dryness  in  a  porcelain  or  platinum  dish.  The  residue 
is  boiled  with  water,  and  filtered,  in  order  to  separate 
a  deposit  of  arseniate  of  iron.  A  solution  of  basic 
phosphate  of  soda  is  then  poured  into  the  filtrate,  and 
there  is  produced  a  precipitate  of  basic  phosphate  of 
cobalt,  which  is  violet,  but  may  become  of  a  pink 
color  by  remaining  under  water. 

This  precipitate  is  washed  and  collected  upon  a 
filter.  While  it  is  still  gelatinous,  one  part  of  it  is 
thoroughly  mixed  with  eight  parts  of  hydrated  alu- 
mina, recently  precipitated  from  a  solution  of  potassa 
alum  by  ammonia.  The  mixture  is  first  dried  in  a 
stove-room,  or  upon  a  furnace,  until  it  is  dry  enough 
to  be  brittle.  It  is  then  calcined  at  a  cherry-red 
heat  for  half  an  hour,  in  a  covered  clay  crucible.  The 
resulting  blue  color  is  kept  in  glass  jars. 

The  operation  will  always  be  successful,  if  the 
alumina  has  been  prepared  with  a  sufficient  excess  of 
ammonia,  and  if  it  has  been  washed  several  times 
with  very  clear  water. 

In  this  preparation  of  cobalt  blue,  the  phosphate  of 
cobalt  may  be  replaced  by  the  arseniate  of  cobalt. 
But,  instead  of  one  part  of  the  violet  precipitate  of 
phosphate  of  cobalt,  one-half  part  of  the  arseniate 
will  be  sufficient  for  eight  parts  of  gelatinous  alu- 
mina. The  arseniate  of  cobalt  can  be  obtained  by 
precipitating  the  solution  of  cobalt  with  one  of  arseni- 
ate of  potassa. 

As  the  gelatinous  alumina,  necessary  for  the  manu- 
facture of  cobalt  blue,  enters  into  the  preparation  of 


BLUE  COLORS. 


259 


several  other  colors,  we  shall  here  explain  its  prepara- 
tion. The  alum  is  dissolved  in  a  quantity  of  v^ater, 
at  least  three  times  that  strictly  necessary  for  the 
solution,  and  is  then  precipitated  by  an  excess  of 
ammonia.  After  stirring,  the  precipitate  is  left  to 
settle,  and  the  liquor  is  decanted  with  a  siphon. 
Several  washings  are  made  with  pure  water,  and  the 
liquors  are  decanted  or  siphoned  off.  Lastly,  the 
residue  of  gelatinous  alumina  is  collected  upon  a 
filter. 

Cobalt  blue,  mixed  with  whites,  gives  light  blue 
tones,  with  a  slightly  violet  tinge.  It  is  very  durable, 
becomes  more  intensely  colored  in  the  air,  and  resists 
the  action  of  fire,  acids,  and  alkalies. 

The  beauty,  or  rather  the  intensity,  of  Thenard 
blue,  depends  on  the  proportions  of  alumina  added. 
With  equal  parts  of  phosphate  of  cobalt  and  of 
hydrated  alumina,  the  blue  is  greenish ;  with  four  to 
five  parts  of  alumina  to  one  of  phosphate,  the  blue  is 
pure.  Intermediate  tones  and  hues  will  be  obtained 
by  varying  the  proportions. 

Several  modifications  have  been  introduced  in  the 
manufacture  of  cobalt  blue,  the  most  important  of 
which  is  that  of  Mr.  Binder,  described  in  the  Tecli- 
nologiste^  v.  5,  page  55. 

"  I  dissolve  6  kilogrammes  of  alum,  free  from  iron, 
in  a  vessel  of  lead  or  earthenware,  and  filter  the  boil- 
ing solution  into  a  wooden  tub,  1.7  metre  high  and  1 
metre  in  diameter,  one-third  filled  with  pure  water. 
I  then  precipitate  the  alumina  with  a  solution  of 
potassa ;  the  tub  is  filled  with  water,  and,  after  set- 
tling and  decantation  of  the  clear  liquor,  I  add  a  new 
quantity  of  water,  and  so  on,  until  the  washings  no 
longer  precipitate  by  the  chloride  of  barium. 


260 


MANUFACTURE  OF  COLORS. 


"I  dissolve  500  grammes  of  sesquioxide  of  cobalt 
in  1500  grammes  of  hydrochloric  acid  at  22°  Be.,  and 
evaporate  the  solution  to  dryness.  The  residue  is 
again  dissolved  in  3  kilogrammes  of  hydrochloric 
acid,  and  a  stream  of  sulphuretted  hydrogen  is  passed 
through  it,  in  order  to  separate  the  foreign  metals 
vrhich  may  be  present.  I  filter,  evaporate  again  to 
dryness,  and  dissolve  the  residue  in  enough  water  to 
obtain  from  4.5  to  5  kilogrammes  of  solution. 

"  When  these  two  preliminary  operations  are  com- 
pleted, I  precipitate  8,  4,  5,  or  6  kilogrammes  of  the 
cobalt  solution  (according  to  the  intensity  of  colora- 
tion desired)  with  ammonia.  A  too  great  excess  of 
this  reagent  is  to  be  avoided,  because  it  may  redis- 
solve  the  cobalt.  After  the  precipitate  has  been 
thoroughly  washed,  I  pour  it  into  the  water  which 
holds  the  divided  alumina  in  suspension.  The  mix- 
ture should  be  constantly  stirred  for  at  least  half  an 
hour,  in  order  to  have  a  perfect  mixture  of  the  two 
precipitates. 

"If  the  supernatant  liquid  be  of  a  reddish  hue,  it 
is  a  proof  that  a  small  proportion  of  cobalt  has  been 
dissolved.  A  little  ammonia  is  then  added,  and  the 
precipitate  is  allowed  to  settle.  After  decantation, 
a  new  quantity  of  water  is  added,  and  so  on,  several 
times.  The  precipitate  is  collected  in  a  fine  cloth 
bag,  drained,  pressed,  and  dried  in  a  stove-room. 
Lastly,  it  is  calcined  at  a  red  heat  for  two  or  two  and 
one-half  hours,  in  clay  crucibles. 

"After  cooling,  the  color  is  finely  ground  in  a  mill, 
dried,  ground  again  upon  a  slab,  and  sifted.  6  kilo- 
grammes of  the  cobalt  solution  give  the  finest  color, 
and  3  kilogrammes  the  clearest." 

It  has  also  been  proposed  to  replace  alumina  by 


BLUE  COLORS.  261 

lime,  in  the  manufacture  of  cobalt  blue.  Mr.  Boullai- 
Marillac,  the  inventor  of  the  process  by  which  the 
color  obtained  is  a  phosphate  of  lime  and  of  oxide  of 
cobalt,  claims  that  the  product  is  richer  and  more 
velvety  in  appearance  than  the  Thenard  blue. 

§  7.  Blue  liydr cited  oxide  of  co2:>per,    Peligot  hlue. 

The  hydrated  oxide  of  copper,  precipitated  from 
the  solution  of  a  copper  salt,  by  an  excess  of  potassa 
or  soda,  becomes  black  rapidly,  even  if  the  washing 
be  effected  with  cold  water.  Mr.  Peligot,  in  1858, 
succeeded  in  obtaining  a  blue  hydrated  oxide  of 
copper,  which  resists  boiling  water,  and  may  be 
heated  at  100°  C,  without  being  altered.  It  is  true 
that  it  retains  traces  of  ammonia,  but  the  proportion 
is  no  greater  than  that  of  the  foreign  matters  always 
found  in  precipitated  oxides. 

Mr.  P61igot  prepares  his  blue  with  all  the  soluble 
salts  of  copper,  the  sulphate  being  preferred.  A  very 
dilute  solution  of  the  copper  salt  is  treated  with  an 
excess  of  ammonia,  and  then  precipitated  by  potassa 
or  soda.  Instead  of  aqua  ammonia,  an  ammoniacal 
salt  may  be  employed.  The  same  color  is  also  pro- 
duced by  adding  a  large  quantity  of  water  to  a 
slightly  ammoniacal  solution  of  nitrate  of  copper. 

The  color  is  not  so  deep  as  that  of  English  blue 
ashes,  but  it  is  purer. 

Concentrated  aqua  ammonia  dissolves  from  seven 
to  eight  per  cent,  of  this  hydrate,  and  this  liquor  is 
the  best  dissolvent  for  cellulose  and  other  substances 
more  or  less  soluble  in  the  reagent  of  Mr.  Schweitzer, 
that  is,  an  ammoniacal  solution  of  oxide  of  copper. 


262 


MANUFACTURE  OF  COLORS. 


§  8.  Blue  of  manganate  of  lime. 

Mr.  Kuhlmann  made,  in  1841,  a  series  of  experi- 
ments for  extracting  potassa  from  feldspar  in  an 
economical  way.  The  best  results  were  obtained  by 
melting  powdered  feldspar  with  chloride  of  calcium. 
It  was  possible  to  extract,  by  this  method,  twenty 
parts  of  chloride  of  potassium  from  certain  kinds  of 
feldspar. 

"While  trying  economical  processes  for  the  prepara- 
tion of  the  chloride  of  calcium,  Mr.  Kuhlmann  calcined 
in  large  furnaces  a  mixture  of  chalk  and  of  the  resi- 
dues of  the  manufacture  of  chlorine,  which  are  com- 
posed of  chloride  of  manganese  and  of  a  certain  pro- 
portion of  chloride  of  iron.  The  result  of  this  calci- 
nation is  a  mass  of  chloride  of  calcium,  colored  green 
by  a  protoxide  of  manganese. 

During  the  repairs  made  on  a  furnace,  employed 
for  six  months  in  effecting  these  calcinations,  Mr. 
Kuhlmann  remarked  that  in  the  mass  of  chloride  of 
calcium  nearest  the  fireplace,  and  where  the  heat  was 
the  greatest  and  oxidizing,  there  were  cavities  filled 
with  magnificent  black  crystals,  whereas  the  super- 
ficial portions  of  the  mass  were  of  the  brightest  blue. 

The  black  crystals  are  formed  of  a  certain  oxide  of 
manganese,  with  3.5  per  cent,  of  oxide  of  iron,  and 
their  composition  corresponds  to  the  natural  ore, 
called  pseudo-morphic  Hausmannite  or  acerdese. 

Mr.  Kuhlmann  ascertained  that  the  blue  substance 
was  a  manganate  of  lime,  which,  on  account  of  its 
magnificent  coloration,  should  attract  the  attention 
of  chemists.  All  the  attempts  made  up  to  the  present 
day,  by  Messrs.  Chevillot,  Edwards,  Forchhammer, 


BLUE  COLORS. 


263 


and  Fromherz,  in  order  to  prepare  it,  have  been 
unsuccessful. 

In  the  opinion  of  Mr.  Kuhlmann,  the  formation  of 
this  manganate  is  probably  due  to  the  decomposition 
of  the  chloride  of  calcium  by  steam,  and  to  a  certain 
solution  of  the  lime  in  the  undecomposed  chloride  of 
calcium.  Baron  Liebig  attributes  the  alkalinity  of  a 
solution  of  chloride  of  calcium,  to  the  partial  decom- 
position of  the  chloride  in  water.  Mr.  E.  Krauss  has 
stated  that  the  decomposition  is  the  greater,  as  the 
chloride  has  been  oftener  moistened  with  water  and 
then  calcined.  Lastly,  Mr.  Pelouze  has  recently 
pointed  out  the  rapid  decomposition  of  chloride  of 
calcium,  under  the  influence  of  steam  at  a  high  tem- 
perature. 

If  the  attempts  for  obtaining  the  manganate  of  lime 
have  been  unsuccessful,  it  is  due,  according  to  Mr. 
Kuhlmann,  to  the  lime  not  being  under  so  favorable 
conditions  for  acting  upon  the  manganese  oxide,  as 
when  it  is  in  solution  in  the  chloride  of  calcium. 

A  great  solubility  is  not  necessary  to  explain  the 
reaction,  because  we  may  admit  that  once  a  portion 
of  lime  becomes  transformed  into  manganate,  another 
equal  portion  will  dissolve  in  the  chloride. 

Such  as  it  is  accidentally  produced  in  reverberatory 
furnaces,  the  manganate  of  lime  is  of  an  ultramarine 
blue  and  appears  crystalline.  It  is  insoluble  in  water, 
although  not  durable  when  in  contact  with  it.  Like 
all  manganates,  it  is  easily  transformed  into  a  per- 
manganate under  the  influence  of  weak  acids,  and 
even  of  carbonic  acid. 

When  the  arts,  Mr.  Kuhlmann  concludes,  by  ap- 
propriate proportions  and  apparatus,  shall  have  suc- 
ceeded in  manufacturing  a  cheap  manganate  of  lime, 


264 


MANUFACTURE  OF  COLORS. 


they  will  have  become  enriched  with  a  most  precious 
agent  for  discoloration  and  disinfection. 

§  9.  Indigo. 

It  was  only  about  the  middle  of  the  sixteenth  cen- 
tury, that  indigo  was  brought  from  India  to  Europe. 
This  coloring  substance  is  furnished  by  the  leaves  of 
several  plants,  called  Indigotifera^  on  account  of  this 
property.  The  plants  most  generally  employed  for 
its  preparation  are — 

1.  Indigotifera  argentea,  or  wild  indigo.  Its  yield 
in  indigo  is  less  than  that  of  the  other  plants,  but  in 
quality  it  is  the  best. 

2.  Indigotifera  tinctoria,  or  French  indigo.  It  pro- 
duces the  greatest  proportion  of  color,  but  in  regard 
to  quality  it  comes  the  last. 

3.  Indigotifera  dispei^ma  or  guatemala.  This  plant 
grows  higher  and  is  more  ligneous.  The  quality  of 
its  indigo  is  better  than  that  of  the  preceding. 

4.  Indigotifera  anil  or  anil.  Its  indigo  is  the  least 
oxidized. 

5.  Lastly,  the  polygonum  tinctorium,  the  cultivation 
of  which  is  recommended  in  France,  the  nerium  tine- 
torium,  and  many  other  plants. 

The  greater  part  of  these  plants  are  indigenous  to 
India  and  Mexico,  and  have  been  introduced  into  the 
two  continents  of  America,  into  China,  Japan,  Mada- 
gascar, Egypt,  etc.  They  belong  to  the  Diadelphia 
decandria  of  Linnaeus,  of  the  family  of  Leguminous 
plants.  The  indigo  is  extracted  from  these  plants  in 
the  following  manner :  when  the  leaves  have  attained 
their  maturity,  they  are  collected,  washed,  cut,  and 
placed  in  tanks  with  a  certain  proportion  of  water. 
They  are  kept  down  by  means  of  boards  loaded  with 


BLUE  COLORS. 


265 


stones.  The  fermentation  soon  begins,  the  liquor  be- 
comes green  and  acid,  and  a  great  number  of  bubbles 
and  rainbow  colored  particles  rise  to  the  surface. 
The  liquor  is  then  run  into  a  lower  tank,  where  it  is 
stirred,  and  the  indigo  is  separated  by  the  addition  of 
a  sufficient  quantity  of  lime-water.  The  deposit  is 
washed  several  times  with  water,  and  dried  in  the 
shade. 

Pure  indigo  is  firm,  odorless,  and  tasteless,  of  a 
violet-blue  color,  unaltered  in  the  air,  insoluble  in 
water  and  ether,  and  but  slightly  soluble  in  boiling 
alcohol,  from  which  it  separates  by  cooling.  It  is 
easily  decolorized  by  chlorine,  and  according  to  cer- 
tain experiments,  by  essence  of  turpentine.  If  it  be 
heated  in  a  retort,  a  portion  is  volatilized  and  con- 
denses in  the  shape  of  copper-colored  needles,  while 
the  remainder  is  decomposed.  Weak  acids  do  not 
dissolve  it,  but  nitric  acid  transforms  it  into  a  yellow 
and  bitter  principle.  It  is  easily  dissolved  by  con- 
centrated sulphuric  acid.  Cold  hydrochloric  acid 
does  not  react  upon  indigo,  but,  with  the  aid  of  heat, 
it  acquires  a  yellow  color,  due  to  the  decomposition 
of  a  small  quantity  of  indigo. 

Indigo  loses  its  blue  color  by  a  protracted  contact 
with  deoxidizing  substances.  Deoxidized  indigo  is 
soluble  in  water,  especially  with  the  aid  of  alkalies. 
When  kept  in  suspension  in  water,  it  is  deoxidized 
by  sulphuretted  hydi'Ogen,  hydrosulphate  of  ammonia 
(sulphide  of  ammonium),  protosulphate  of  iron  (green 
copperas),  potassa,  and  the  protoxide  of  tin.  In 
dyeing  operations  it  is  generally  deoxidized  with  the 
following  substances : — 


266 


MAl^UFACTURE  OF  COLORS. 


Protosulphate  of  iron 
Slaked  lime  . 
Finely  powdered  indigo  . 
Water     .       .       .  . 


3  " 
1  " 
150  " 


2  parts. 


All  of  these  substances  are  put  into  a  glass  matrass, 
and  are  kept  there  for  several  hours  at  a  temperature 
of  40°  to  50°  C.  The  lime  forms  with  the  sulphuric 
acid  an  insoluble  sulphate  of  lime,  and  the  protoxide 
of  iron  is  precipitated  as  peroxide  after  having  taken 
the  oxygen  from  the  indigo.  The  blue  color  is 
restored  by  an  oxidation  resulting  from  exposure  to 
the  air.  The  solution  of  indigo  in  sulphuric  acid  is 
deoxidized  by  iron  filings  or  zinc. 

Commercial  indigo  is  never  pure,  and  the  pure 
article  is  obtained  by  sublimation  in  closed  vessels, 
the  sublimate  being  in  needle-like  crystals.  The 
fracture  of  good  indigo  is  smooth,  and  the  portion 
rubbed  w^ith  a  finger-nail  acquires  a  coppery  lustre. 
The  qualities  generally  preferred  are  light,  and  with 
a  deep  and  bright- violet  blue  color. 

There  are  in  the  trade  at  least  sixty  varieties  of 
indigo,  the  better  known  of  which  are  denominated 
by  the  names  of  the  countries  they  come  from, 
thus : — 

1.  Indian  indigo  is  called  Bengal,  Madras,  Ooro- 
mandel,  etc. 

2.  Guatemala  indigo,  indigo  fiore ;  this  is  the  most 
esteemed  of  all. 

According  to  Mr.  Chevreul,  commercial  indigo  is 
composed  of — an  immediate  principle  (indigotin), 
a  red  resin  soluble  in  water,  a  greenish-red  substance 
soluble  in  water,  carbonate  of  lime,  alumina,  silica^ 
and  oxide  of  iron. 


BLUE  COLORS. 


267 


Berzelius  has  found  in  it — gluten,  brown,  red,  and 
blue  coloring  principles,  fecula,  silica,  alumina,  oxide 
of  iron,  and  lime. 

According  to  Messrs.  Dumas  and  le  Eoyer,  pure 
indigo  is  composed  of — 


Indigo  is  generally  applied  with  size,  because  oil 
renders  it  black  or  green.  It  possesses  less  bright- 
ness than  Prussian  blue.  Mixed  with  a  white,  the 
resulting  blue  is  grayish,  and  the  exterior  becomes 
decolorized. 

Indigo  is  sometimes  adulterated  with  various  sub- 
stances. Prussian  blue  is  detected  with  a  caustic 
lye  of  potassa,  the  color  of  the  sample  losing  part  of 
its  intensity.  Pure  indigo  is  not  acted  upon  by  this 
solution.  Fuming  sulphuric  acid  decolorizes  Prus- 
sian blue,  and  dissolves  the  indigo  without  changing 
its  color.  Chlorine  decolorizes  indigo,  and  has  no 
immediate  action  upon  Prussian  blue.  Lastly,  if  the 
suspected  sample  be  burned,  and  the  ashes  be  treated 
with  hydrochloric  acid,  the  solution  will  give  with 
ammonia  and  the  ferrocyanide  of  potassium,  charac- 
teristic tests  of  the  presence  of  iron,  should  Prussian 
blue  be  present.  The  proportion  and  the  appearance 
of  the  ashes  give  also  good  indications  as  to  the 
quality  of  the  indigo. 

Indigo,  on  account  of  its  high  price,  and  of  the 
indefinite  color  of  its  mixtures,  is  not  employed  by 
painters.  It  is  used  by  manufacturers  of  paper 
hangings. 


Nitrogen  . 
Hydrogen 
Oxygen  . 


Carbon 


Y3.26 
13.75 
2.83 
10.16 


100.00 


268 


MA]S"CJFACTURE  OF  COLORS. 


§  10.  Blue  carmine^  indigo  carmine^  Uue  of  Migland 

or  Holland, 

Nordhausen  sulphuric  acid  dissolves  indigo  almost 
entirely.  In  accordance  with  the  proportions  of  acid 
held  in  it,  this  solution  bears  different  names.  Thus, 
indigo  imrple  is  formed  of  equal  equivalents  of  acid 
and  indigo ;  eight  to  ten  parts  of  indigo,  and  sixteen 
to  twenty  of  sulphuric  acid,  constitute  indigo  carmine 
or  sulphoindigotic  acid.  Generally,  painters  mingle 
these  two  solutions  under  the  names  of  Saxony  blue, 
Hue  in  liquor,  and  composition  blue. 

A  blue  carmine  is  sometimes  employed  in  painting, 
which  is  obtained  by  precipitating  Saxony  blue  or 
the  blue  in  liquor  by  potassa.  The  operation  is  as 
follows : — 

A  frigorific  mixture  is  made  with  common  salt  and 
broken  ice,  in  which  there  is  placed  a  vessel  holding  4 
kilogrammes  of  fuming  sulphuric  acid.  1  kilogramme 
of  finely  powdered  indigo  is  then  added  to  the  acid, 
by  small  portions  at  a  time,  and  stirred  all  the  while. 
"When  the  solution  is  complete,  the  clear  liquor  is 
decanted,  and  a  solution  of  tartrate  of  potassa  is 
added  to  it  until  precipitation  no  longer  takes  place. 
After  settling  and  decanting,  the  precipitate  is  col- 
lected and  washed  with  cold  water  until  the  wash- 
ings cease  to  be  acid.  The  color  is  then  drained 
upon  a  filter,  and  dried  in  the  dark.  Blue  carmine 
has  a  very  bright  bluish  hue,  which  does  not  stand 
the  action  of  light.  It  is  employed,  with  size,  in  the 
manufacture  of  artificial  flowers. 

There  is  also  a  color,  called  blue  of  England,  blue 
of  Holland,  and  plait  of  indigo,  which  is  fine  enough, 
but  wanting  in  durability.    It  is  a  mixture,  in  unde- 


BLUE  COLORS. 


269 


termined  proportions,  of  Prussian  blue,  indigo,  smalt, 
chalk,  and  starch,  which  is  thickened  and  rendered 
homogeneous  with  a  mucilage  of  rice  flour,  and  dried 
in  the  shape  of  lumps  or  troches. 

One  of  the  reasons  why  indigo  carmine  is  often  sold 
in  the  pasty  shape,  is  that  it  becomes  covered  with  a 
white  efflorescence,  when  it  has  been  dried  and  kept 
for  some  time.  This  efflorescence  is  due  to  salts  in 
the  waters  employed  for  washing,  which  salts  are  left 
purposely,  in  order  to  prevent  a  loss  of  carmine,  which 
is  soluble  in  pure  water.  However,  the  pasty  state 
is  objectionable  on  account  of  the  greater  difficulty 
and  cost  in  transportation,  and  of  the  opportunity 
of  adding  an  excess  of  water.  By  the  experiments  of 
Mr.  J.  J.  Pohl,  it  is  demonstrated  that  a  small  quan- 
tity of  glycerin  will  prevent  the  efflorescence  of 
indigo  carmine,  and  will  permit  it  to  be  kept  for 
years  without  any  deleterious  effect  upon  the  beauty 
of  the  product,  or  upon  the  colors  it  produces  on 
tissues.  An  addition  of  3  to  4  per  cent  of  glycerin, 
calculated  from  the  weight  of  dry  carmine,  is  sufficient 
to  arrive  at  that  result,  and  tlie  present  low  price  of 
glycerin  cannot  be  a  bar  to  this  mode  of  preservation. 

§  11.  Ultramarine  hlues. 

The  coloring  substance  known  under  the  name  of 
ultramarine  blue,  has  been  the  subject  of  a  great  num- 
ber of  chemical  researches.  The  operations  of  the 
chemists  have  been  of  two  kinds :  first,  analysis  has 
been  resorted  to,  in  order  to  arrive  at  the  composition 
of  the  native  ultramarine ;  second,  from  the  synthesis 
of  the  results  obtained,  there  has  resulted  an  artificial 
preparation  of  a  similar  compound. 

1 


270 


MANUFACTURE  OF  COLORS. 


1st.  Real  or  Native  Ultramarine  Blue. 

Ultramarine  is  extracted  from  lazulite^  lapis  lazuli^ 
or  azure  hlue  lazulite,  a  mineral  which  belongs  to  the 
granitic  rocks.  This  substance,  which  is  remarkable 
for  its  fine  azure-blue  color,  is  not  altered  even  by  a 
violent  fire. 

TJltramarine-lazulite  is  generally  found  in  rolled 
and  scattered  lumps ;  the  finest  comes  from  Prussia, 
China,  and  the  Great  Bucharia.  It  is  a  dense  and 
opaque  stone,  of  a  pure  or  dirty  blue  color,  and  gold 
spangles  are  scattered  in  the  gangue.  The  ultrama- 
rine blue  is  separated  from  this  stone  by  the  follow- 
ing process,  indicated  by  Thenard :  The  stone  is 
disintegrated  by  being  brought  to  a  red  heat,  and 
then  thrown  into  cold  water ;  it  is  afterwards  pow- 
dered and  intimately  mixed  with  twice  its  weight  of 
a  mastic,  composed  of  resin,  wax,  and  boiled  linseed 
oil.  The  resulting  paste  is  wrapped  in  a  cloth, 
and  kneaded  in  hot  water  several  times,  in  order  to 
express  the  color.  The  first  water  is  generally  dirty 
and  thrown  away  ;  the  second  gives  a  blue  of  the  first 
quality;  the  third  a  blue  inferior  to  the  former;  the 
fourth  water  a  still  inferior  product,  and  so  on,  until 
the  product  is  so  pale,  that  it  is  called  ultramarine 
ash.  These  liquors  are  allowed  to  settle,  and  the 
different  blues  require  but  another  finer  grinding, 
effected  with  the  greatest  cleanliness,  before  they  are 
dried.  This  operation  is  based  upon  the  property  of 
ultramarine  blue,  of  being  less  adhering  to  the  mastic 
than  the  foreign  matters  with  which  it  is  associated. 

Thenard  observes,  that  if,  as  is  customary  with 
certain  color  manufacturers,  the  hot  red  stone  be 
thrown  into  vinegar,  instead  of  water,  the  yield  will  be 


BLUE  COLOKS. 


271 


diminished,  because  the  acid,  although  weak,  attacks 
the  color  at  a  high  temperature. 

As  ultramarine  blue,  on  account  of  its  variety, 
beauty,  and  durability,  is  exceedingly  costly,  and, 
according  to  Thenard,  is  sold  at  prices  ranging  from 
80  to  200  francs  per  30  grammes,  it  is  not  employed 
for  ordinary  painting. 

It  will  be  easy  to  ascertain  whether  ultramarine  is 
mixed  with  cobalt  blue,  by  digesting  a  pinch  of  the 
sample  in  nitric  acid.  After  a  little  while,  the  ultra- 
marine is  entirely  decolorized,  while  the  cobalt  retains 
its  blue  color. 

It  may  also  happen  that  ultramarine  is  adulterated 
by  Prussian  blue  and  indigo.  The  latter  substance 
will  be  detected  by  placing  a  small  quantity  of  the 
sample  upon  incandescent  charcoal,  and  there  is 
produced  a  bluish  vapor,  accompanied  by  the  cha- 
racteristic smell  of  burning  indigo.  If  the  sample  be 
treated  at  a  moderate  temperature  with  ammonia,  the 
Prussian  blue  is  decomposed,  but  its  color  will  reap- 
pear by  pouring  into  the  liquor  a  few  drops  of  acid 
nitrate,  persulphate,  or  perchloride  of  iron. 

"  The  preparation  of  native  ultramarine,"  says  Mr. 
Brunner,  "  is  effected  mostly  by  mechanical  processes, 
tending  to  separate  it  from  the  foreign  matters. 
Although  the  methods  may  differ  in  certain  particu- 
lars, they  are  all  based  upon  a  levigation  (floating)  of 
the  powdered  substance. 

"  When  lazulite,  after  several  calcinations,  followed 
by  immersions  in  cold  water,  has  become  sufficiently 
brittle,  it  is  finely  ground.  This  powder  is  combined 
with  a  fused  mixture  of  wax,  resin,  pitch,  and  oil, 
and  then  worked  with  hot  water  in  a  stone  mortar. 
The  mineral  gangue  settles,  while  the  ultramarine 


272 


MANUFACTURE  OP  COLORS. 


remains  suspended  in  the  liquid.  By  repeating  this 
operation  several  times  with  the  proper  care,  the  blue 
colored  substance  is  separated  as  completely  as  prac- 
ticable, and  it  is  sorted  into  different  qualities,  which 
are  sold  at  different  prices.  The  inferior  quality,  con- 
taining a  certain  proportion  of  gangue,  is  called  ultra- 
marine ash.  The  high  price  of  the  first  quality,  be- 
sides the  cost  of  a  long  and  tedious  labor,  is  due 
especially  to  the  small  amount  collected,  that  is, 
according  to  Clement  and  Desormes,  from  two  to 
three  per  cent,  of  the  best  kizulite. 

"  We  owe  the  first  analysis  of  this  substance  to  the 
two  afore-named  chemists,  who  have  found  in  it — 


Silica   35.8 

Alumina  34.8 

Soda   23.2 

Sulphur  3.1 

Carbonate  of  lime  '  .3.1 


100.0 

"Many  years  after,  C.  G.  Gmelin  made  a  new 
analysis  of  a  sample  of  average  quality,  obtained 
from  Paris.    The  composition  was — 


Silica   4Y.306 

Alumina   22.000 

Soda  (with  potassa)   12.063 

Lime    1-546 

Sulphuric  acid   4.679 

Sulphur   0.188 

Water,  resinous  matter,  and  loss  .       .       .       .  12,218 


100.000 

"  I  am  not  acquainted  with  other  analyses  of  ultra- 
marine, except  those  just  indicated.  On  the  other 
hand,  several  analytical  researches  have  been  made 
upon  the  lazulite  itself,  the  mineral  which  furnishes 


BLUE  COLORS. 


273 


this  expensive  color.  Although  it  is  impossible  to 
draw  rational  conclusions  from  analyses  made  with 
different  samples  of  such  a  complicated  mineral, 
nevertheless  the  effort  has  been  made  to  arrive  by 
this  process  at  some  indications  upon  the  nature  of 
the  coloring  substance.  Here  are  the  results  of  these 
analyses  : — 


Klaproth.  L. 

Gmelin. 

Varrentrapp. 

Silica 

.  46.0 

49 

45.50 

Alumina  . 

.  14.5 

11 

31.Y6 

Soda 

8 

9.09 

Lime 

.  n.5 

16 

3.52 

Sulphur  . 

0.95 

Sulphuric  acid  . 

.  4.0 

2 

5.89 

Oxide  of  iron  . 

.  3.0 

4 

0.86  (metal) 

Chlorine  . 

0.42 

Water 

.  2.0 

0.12 

Carbonic  acid  . 

.  10.0 

Magnesia  . 

.2 

"The  most  important  technical  question  was,  to 
ascertain  which  were  the  elements  composing  the  blue 
color.    On  this  subject  opinions  differed. 

"Margraff,  who,  as  early  as  1758,  had  published  a 
few  researches  upon  lazulite,  combated  the  opinion, 
then  general,  that  this  mineral  contained  copper;  but 
at  the  same  time  he  thought  that  the  color  was  due 
to  iron. 

"  Guyton-Morveau  believed  that  the  coloring  prin- 
ciple was  a  sulphide  of  iron,  and  many  chemists  were 
of  the  same  opinion.  Even  more  recently,  Mr.  Var- 
rentrapp was  of  the  same  belief,  although  Clement  & 
Desormes  certified  that  not  a  trace  of  iron  was  found 
in  a  fine  sample  of  ultramarine.  But  the  latter 
chemists  say  nothing  about  the  nature  of  the  color- 
ing material." 
18 


274 


MANUFACTURE  OF  COLORS. 


2d.  Artificial  Ultramarine. 

A  few  accidental  observations  gave  the  idea  of 
undertaking  researches  upon  the  artificial  preparation 
of  a  substance  similar  to  the  coloring  material  of 
lazulite. 

Thus  Goethe,  in  his  travels  in  Italy  (Palermo, 
*  April  13th,  1787),  mentions  that  in  Sicily  they  use  a 
certain  vitreous  substance  formed  in  lime-kilns.  It 
is  sawed  into  slabs,  which  are  used,  instead  of  lapis 
lazuli,  for  the  decoration  of  altars,  mausolea,  and 
other  ornaments  of  religious  temples. 

Another  observation,  made  by  Tessart,  in  a  French 
soda-works,  gave  more  precise  data  upon  the  possi- 
bility of  forming  a  blue  combination,  similar  to  ultra- 
marine. This  manufacturer  had  noticed  that  a  sub- 
stance of  a  fine  blue  color  was  formed  in  the  soda 
furnace,  when  a  certain  kind  of  sandstone  had  been 
employed  for  its  construction  ;  but  that  the  color  dis- 
appeared when  bricks  were  the  building  material. 
Vauquelin  found  in  this  blue  compound,  separated 
from  about  44  per  cent,  of  sand  mechanically  mixed, 
sulphate  of  lime,  sulphate  of  soda,  chloride  of  sodium, 
silica,  alumina,  and  a  small  proportion  of  sulphur  and 
iron;  and,  from  this  analysis,  he  demonstrated  the 
analogy  existing  between  this  compound  and  the 
native  ultramarine. 

Therefore,  there  remained  but  to  discover,  by  syn- 
thetical researches,  a  method  by  which  such  a  com- 
pound could  be  reproduced,  and  the  problem  was 
resolved  in  France.  Mr.  Guimet  was  the  first  to  put 
into  the  market  a  product  nearly  as  fine  as  real  ultra- 
marine, and,  at  the  present  time,  he  still  manufactures 
one  of  the  finest  known. 


BLUE  COLORS. 


275 


Savans  and  manufacturers  worked  the  subject  with 
great  energy,  and  the  latter,  possibly  in  an  empirical 
manner,  but  certainly  after  analytical  researches, 
discovered  several  processes  for  preparing  products 
which  are  now  abundant  in  the  trade.  It  is  but 
natural  that  few  precise  data  have  been  made  known, 
because  it  is  not  customary  for  manufacturers  to 
publish  their  processes.  But  it  is  certain  that  these 
processes  are  sure,  and  improved,  if  we  judge  from 
the  fine  qualities  of  ultramarine  which  are  now  in  the 
market,  and  at  very  moderate  prices. 

Without  any  doubt,  this  manufacture  has  been 
greatly  aided  by  the  publication,  in  1828,  of  a  memoir 
of  C.  G.  Gmelin,  in  which  this  chemist  gives  a  precise 
formula  for  the  preparation  of  artificial  ultramarine. 
But,  although  it  may  be  true  that  this  formula  is  not 
to  be  trusted  in  every  particular,  or  that  it  does  not 
always  furnish  an  identical  product,  or  that  it  does 
not  admit  of  its  manufacture  at  the  present  low  prices, 
it  is  but  justice  to  assert  that  this  memoir  must  have 
been  the  point  of  departure  for  all  the  researches 
made  up  to  the  present  time. 

More  recently,  Messrs.  Eisner  and  Yarrentrapp 
have  published  the  analysis  of  two  kinds  of  artificial 
ultramarine.  Here  are  the  results  of  their  re- 
searches : — 


Varrentrapp. 

Eisner. 

Soda 

.  21.416 

33.00 

Potassa 

.  1.152 

Lime 

.  0.021 

Alumina 

.  23.304 

20.50 

Silica 

.  45.604 

40.00 

Sulphuric  acid  . 

.  3.830 

3.40 

Sulphur 

.  1.685 

4.00 

Iron  . 

.  1.063 

1.00  oxide. 

Chlorine 

Traces. 

276 


MANUFACTURE  OF  COLORS. 


The  formula  given  by  Gmelin  for  the  chemical 
preparation  of  ultramarine,  may  be  condensed  as 
follows : — 

Gelatinous  silica  (prepared  in  the  ordinary  manner 
from  a  natural  silicate)  is  dissolved  in  a  solution  of 
caustic  soda,  and  pure  hydrated  alumina  is  added, 
until  the  proportions  amount  to  thirty -five  parts  of 
anhydrous  silica,  and  thirty  of  anhydrous  alumina. 
The  mixture  is  evaporated  and  brought,  by  stirring 
carefully,  to  the  state  of  a  dry  powder,  which  is  ground 
and  thoroughly  mixed  with  an  equal  weight  of 
sublimed  sulphur.  There  is  added  to  this  mixture 
another  compound  of  equal  parts  of  carbonate  of  soda 
and  sublimed  sulphur,  equal  in  weight  to  that  of  the 
dry  silico-aluminous  powder.  The  whole  is  then  in- 
troduced into  a  closed  crucible,  and  kept  for  two 
hours  at  a  strong  red  heat.  The  greenish  mass  thus 
obtained  is  again  heated  either  in  crucibles  or  in  clay 
tubes,  but  without  the  access  of  the  air,  until  it  has 
acquired  the  desired  blue  color.  Gmelin  thinks  that 
this  last  operation  is  the  most  difficult,  and  he 
describes  several  modes  of  operation  for  arriving  at  a 
satisfactory  result. 

Lastly,  Gmelin  suggests,  that  in  manufacturing 
operations,  it  may  be  possible  to  replace  the  hydrate 
of  alumina  by  clay,  deprived  of  its  iron  by  a  treat- 
ment with  hydrochloric  acid,  and  afterwards  washed. 

Independently  of  this  formula,  two  more  have  been 
made  known : — 

According  to  Eobiquet,  a  mixture  of  2  parts  of 
kaolin,  3  of  sulphur,  and  3  of  dry  carbonate  of  soda 
are  heated  in  a  clay  retort  until  vapors  cease  to  be 
disengaged.  After  cooling,  the  retort  is  broken,  the 
powdered  mass  is  washed  with  water,  and  the  remain- 


BLUE  COLORS. 


277 


ing  powder  is  heated  again  until  the  sulphur  is 
expelled. 

Tiremon  melted  1075  parts  of  crystallized  carbonate 
of  soda  in  its  water  of  crystallization,  and  added  5 
parts  of  red  sulphide  of  arsenic,  a  quantity  of  gelati- 
nous alumina  equal  to  7  parts  of  calcined  alumina, 
100  parts  of  sifted  clay,  and  221  parts  of  sublimed 
sulphur.  The  mass  was  carefully  evaporated  to  dry- 
ness in  a  crucible,  and  then  calcined  at  a  red  heat. 
Lastly,  the  product  was  kept  again  at  a  dull  red  heat 
in  a  covered  dish,  and  stirred  constantly  for  two 
hours. 

We  shall  now  add  further  particulars  on  each  of 
the  modes  of  preparation,  with  the  exception  of  the 
Guimet  process,  which  is  still  kept  secret. 

A.  Guimet  Process. 

The  Societe  Encouragement  proposed,  in  1824,  a 
premium  for  the  manufacture  of  an  ultramarine  pos- 
sessing all  the  qualities  of  that  extracted  from  lapis 
lazuli.  This  premium  was  awarded  to  Mr.  Guimet, 
on  December  3d,  1828. 

We  here  reproduce  an  extract  from  the  report  made 
by  Mr.  M^rimee,  in  the  name  of  the  committee  on 
chemical  arts. 

"In  1824,  you  proposed  a  premium  of  6000  francs 
for  the  manufacture  of  an  ultramarine  blue  possessing 
all  the  qualities  of  that  extracted  from  lapis  lazuli ; 
this  problem,  to  which  you  attached  great  importance, 
is  completely  resolved. 

"  Mr.  Guimet,  a  graduate  of  the  polytechnic  school, 
obtained,  one  year  ago,  results  which  you  would 
have  applauded,  but  he  thought  that  his  work  was 


278 


MANUFACTURE  OF  COLORS. 


not  complete  as  long  as  he  could  see  new  improve- 
ments. 

"At  that  time  several  artists  made  the  trial  of  his 
ultramarine,  and  certified  that  they  found  it  equal  to 
that  imported  from  Italy.  The  experiment  may  be 
seen  in  the  Apotheosis  of  Horner^  painted  by  Mr, 
Ingres  on  the  ceiling  of  the  gallery  of  the  museum. 
The  drapery  of  one  of  the  principal  figures  is  painted 
with  Mr.  Guimet's  ultramarine,  and  no  other  painting 
presents  such  a  bright  blue. 

"ISTeither  has  your  committee  on  chemical  arts 
neglected  the  experiments  by  which  the  indentity  of 
quality  of  the  new  color  with  that  extracted  from 
lazulite,  may  be  ascertained.  It  has  verified  in  it  all 
the  characteristics  of  a  pure  ultramarine. 

"  This  discovery  will  mark  an  epoch  in  the  history 
of  painting ;  it  is  one  of  which  the  chemical  arts  may 
be  proud,  etc." 

Chaptal,  the  President  of  the  Society,  while  pre- 
senting the  premium  to  Mr.  Guimet,  remarked  that 
Mr.  Horace  Vernet,  in  a  very  large  picture,  the  Battle 
of  Fontenoy^  had  employed  Guimet's  ultramarine  ex- 
clusively, which  he  considers  as  superior  to  that  pre- 
pared from  lazulite. 

So  much  for  the  Guimet  process. 

B.  Gmelin  Process. 

The  process  of  Mr.  Guimet  being  still  kept  a  secret, 
Gmelin,  professor  of  chemistry  at  Tubingen,  has  pub- 
lished the  following  process  for  the  manufacture  of 
ultramarine.  Although  it  may  be  advantageously 
modified  in  several  ways,  we  present  it  as  given  by 
the  inventor. 

~    "  Silica  and  alumina,  in  the  hydrate  state,  are  pre- 


BLUE  COLOKS. 


279 


pared — the  first,  by  smelting  finely  powdered  quartz 
with  four  times  its  weight  of  carbonate  of  potassa, 
dissolving  the  fluid  mass  in  water,  and  precipitating 
by  hydrochloric  acid ;  the  second,  by  precipitating  a 
solution  of  alum  with  ammonia.  These  two  precipi- 
tates should  be  carefully  washed  with  boiling  water. 
Then  the  proportion  of  the  dry  substance  is  deter- 
mined by  calcining  a  small  quantity  of  the  wet  article. 
A  certain  quantity  of  hydrated  silica,  the  weight  of 
which  is  noted  down,  is  dissolved  in  a  solution  of  caus- 
tic soda,  which  should  be  as  saturated  as  practicable. 
For  every  twenty-two  parts  of  silica  (calculated  as 
anhydrous),  there  are  added  seventy  paits  of  alumina 
(also  calculated  as  anhydrous),  and  the  whole  is  evapo- 
rated down  to  the  state  of  a  wet  powder,  taking  care 
to  stir  the  mixture  during  the  whole  operation. 

"  Two  parts  of  sulphur  and  one  of  dry  carbonate  of 
soda  are  gradually  brought  to  a  middling  red  heat  in 
a  Hessian  crucible,  with  a  well  fitting  cover.  When 
the  mass  is  fused,  the  above  mixture  is  projected  into 
it  by  very  small  quantities  at  a  time,  and  before  new 
additions  are  made,  the  effervescence  due  to  the 
escape  of  steam  must  have  ceased.  The  crucible  is 
left  one  hour  longer  at  a  moderate  red  heat,  and  then 
allowed  to  cool  off.  It  contains  ultramarine,  mixed 
with  an  excess  of  sulphide  of  sodium,  which  is 
separated  by  washings.  If  the  color  contains  an 
excess  of  sulphur,  the  latter  is  expelled  by  a  calcina- 
tion at  a  moderate  heat.  If  all  the  portions  of  the 
ultramarine  are  not  thoroughly  calcined,  the  finest 
parts  are  separated  by  levigating  the  finely  powdered 
substance  in  water. 

''Ultramarine  resists  fire  and  alkalies,  but  not  the 
action  of  certain  acids." 


280 


MANUFACTURE  OF  COLORS. 


100  parts. 


7  " 


Dry  carbonate  of  soda  (400  parts),  or  crystallized    .    1075  " 


Mix  with  the  carbonate  of  soda,  melted  in  its  water 
of  crystallization,  the  powdered  sulphide  of  arsenic, 
and  when  the  latter  has  become  partly  decomposed, 
add  the  washed  gelatinous  alumina,  which  is  obtained 
by  the  precipitation  of  alum  with  carbonate  of  soda. 
Lastly,  add  the  clay  and  the  sublimed  sulphur,  which 
have  been  mixed  beforehand.  When  the  mass  has 
become  compact  by  evaporation,  it  is  introduced  into 
a  covered  crucible,  which  is  heated  slowly  at  the 
beginning  in  order  to  expel  all  remaining  dampness, 
and  then  brought  to  a  red  heat.  The  fire  should  be 
conducted  in  such  a  manner  that  the  product  is  agglu- 
tinated (sintered),  but  not  fused. 

After  cooling,  the  product  is  heated  again  to  expel 
the  excess  of  sulphur,  and  then  ground  and  washed  in 
pure  water.  The  powder  which  remains  in  suspen- 
sion in  the  liquid,  is  collected  upon  a  filter.  When 
the  mixture  has  been  well  made  the  whole  may  be 
employed,  otherwise  many  portions  remain  colorless. 
There  are  brown  fragments,  resulting  from  the  corro- 
sion of  the  crucible,  when  the  mixture  has  been  com- 
pletely fused.  These  defects  do  not  appear  if  the 
operation  has  been  conducted  with  the  proper  care. 
The  blue  is  drained  upon  the  filter  without  further 
washings,  and  dried.  The  product  is  of  a  fine  bluish- 
green;  and,  if  it  be  heated  for  some  time,  with  occa- 


Sublimed  sulphur 
Sulphide  of  arsenic 


221  " 
5  " 


BLUE  COLORS. 


281 


sional  stirrings,  it  acquires  a  very  handsome  blue 
color. 

D.  Weger  Process. 

Preparation. — Grind  together  8  parts  of  pure  fer- 
ruginous clay  (bole),  J  part  of  hydrated  alumina,  9 
parts  sublimed  sulphur,  and  8  parts  of  fused  caustic 
soda,  dissolved  in  20  parts  of  water.  "When  a  homo- 
geneous paste  has  been  obtained,  it  is  heated  for  one 
or  two  hours  in  a  glass  or  porcelain  retort,  until  there 
are  no  longer  steam  or  sulphur  fumes  distilled  over. 
The  porous  and  greenish  residue  is  then  calcined  in 
a  Hessian  crucible,  in  order  to  remove  the  excess  of 
sulphur,  and  then  (when  cold)  washed  with  pure 
water.  The  bluish-green  powder  is  again  calcined  in 
a  flat  dish,  which  is  covered  and  brought  to  an 
incipient  red  heat.  During  this  operation,  which 
lasts  about  one  and  a  half  hours,  the  powder  is  con- 
stantly stirred.  Lastly,  the  color  is  washed  and  levi- 
gated (floated). 

When  the  porous  green  mass,  called  ultramarine 
green,  and  obtained  from  the  first  calcination,  is 
broken  into  pieces  of  the  size  of  a  pea,  and  exposed 
to  the  air  for  some  time,  it  becomes  transformed  into 
a  magnificent  ultramarine  lazulite  blue,  under  the 
influence  of  the  dampness  in  the  air. 

When  dry  caustic  soda  is  thoroughly  mixed  with 
the  indicated  proportions  of  clay,  alumina,  and  sul- 
phur, and  the  mixture  packed  tightly  in  a  Hessian 
crucible,  there  is  obtained,  after  one  to  two  hours  of 
calcination  at  a  clear  red  heat,  a  product  which,  when 
cold,  possesses  a  pink-red  hue,  very  handsome  and 
uniform. 

G  reen  ultramarine,  in  the  opinion  of  Mr.  ^iV^eger,  is 


282  MANUFACTURE  OF  COLORS. 


a  combination  of  blue  ultramarine  with  a  double 
proportion  of  sulphur.  Therefore,  by  expelling  the 
excess  of  sulphur  by  calcination,  the  second  color  is 
obtained  from  the  first. 

Vltramarme  for  sprinting, — The  preparation  of  a 
printing  color  with  ultramarine  is  very  simple.  A 
good  quality  of  ultramarine  is  very  finely  ground,  and 
mixed  with  linseed,  or  nut,  or  purified  poppy  oil.  If 
the  latter  cannot  be  had,  some  old  and  perfectly  clear 
oil  may  be  used.  One-twentieth  of  hydrated  alumina, 
like  that  employed  in  the  preparation  of  the  ultrama- 
rine, is  also  added.  Then  a  small  quantity  of  good 
white  Venice  soap  is  finely  ground  upon  the  slab. 
In  order  to  ascertain  whether  a  sufficiency  of  soap 
has  been  added,  a  brush  charged  with  the  color  is 
dipped  into  pure  water,  and  we  observe  whether  the 
color  and  the  water  mix  well  together  or  not.  If  the 
mixing  be  satisfactory,  the  proportion  of  soap  is  suffi- 
cient, because  an  excess  will  change  the  hue  of  the 
color.  However,  in  case  the  printing  mixture  should 
be  too  compact,  a  little  soap  water,  of  which  a  supply 
should  be  kept  at  hand,  may  be  added. 

It  is  possible  to  print  with  this  mixture  upon  tissues 
of  cotton  and  wool,  and  even  upon  silk  and  paper. 
The  color  does  not  become  hard,  as  is  the  case  when 
the  thickening  is  gum. 

Miniature  painting  itself  will  find  in  this  color 
vigorous  and  pure  tones,  and  every  intelligent  artist 
sees  the  advantages  it  presents. 

For  theatrical  decorations  and  paper  hangings, 
where  glue  size  is  employed,  the  above  mixture  can 
be  applied  with  the  greatest  success.  It  will  impart 
iin  unequalled  brightness  and  purity  of  color  to 
flowers,  fruits,  shadows,  etc.,  without  any  danger  of 
the  paint  scaling  off. 


BLUE  COLORS. 


283 


E.  Pruckner  Process. 

Mr.  C.  P.  Pruckner,  manufacturer  at  Hof,  in 
Bavaria,  has  published  a  memoir  on  the  manufacture 
of  ultramarine  blue,  which  has  been  translated  and 
printed  in  the  Technologiste,  v.  6,  pages  299-345.  We 
borrow  from  it  the  following  description,  and  we  note 
that  the  raw  materials  are  clay,  sulphate  of  soda,  char- 
coal, and  an  iron  salt,  which  is  generally  green  vitriol. 

"  The  clay  employed  in  the  manufacture  of  artificial 
ultramarine  has  the  greatest  influence  upon  the  color 
produced ;  and  it  is  likely  that  the  failure  of  many 
experiments  is  due  to  the  use  of  a  clay  holding  too 
much  iron.  I  use  a  white  clay,  remaining  white  after 
calcination,  and  which,  therefore,  contains  very  little 
iron.  It  is  a  kind  of  kaolin,  of  a  dull  color,  which 
sticks  to  the  tongue,  forms  with  water  a  paste  pos- 
sessing little  plasticity,  and  which  is  found  in  the 
principality  of  Peuss,  near  Koschitz.  It  is  employed 
in  'the  manufacture  of  porcelain,  and  contains  from 
forty-two  to  forty-three  per  cent,  of  alumina.  It  is 
evident  that,  the  other  conditions  being  the  same,  the 
more  aluminous  clay  is  to  be  preferred. 

"  In  the  manufactory  of  I^^uremberg,  the  clay  most 
generally  employed  is  a  white  sigillaria  earth  (bolus 
alha),  which  comes  from  Teschenrenth,  in  the  High 
Palatinate. 

"At  Nuremberg,  the  sulphate  of  soda  resulting 
from  the  preparation  of  hydrochloric  acid  is  bought, 
either  already  refined,  or  in  the  crude  state.  In  the 
latter  case,  it  is  refined  in  the  color  works,  and  this 
operation,  which  we  shall  examine  further  on,  is  in- 
tended to  remove  the  free  hydrochloric  acid  and  the 
iron  salts,  which  impair,  and  even  destroy,  the  blue 
color  of  the  ultramarine. 


284  MANUFACTURE  OF  COLORS. 

"  Roll  sulphur  is  too  well  known  to  need  explana- 
tion. 

"  The  charcoal  from  dry  wood  answers  all  that  is 
required  of  it.  Mineral  coal  is  sometimes  employed, 
and  it  should  give  the  least  amount  of  ferruginous 
ashes. 

"The  calcination  of  the  mixtures  is  effected  in 
muffles,  heated  in  a  reverberatory  furnace,  since  it  is 
much  more  easy  to  regulate  the  temperature  and  to 
watch  the  operation,  than  when  crucibles  are  em- 
ployed. These  muffle  furnaces,  in  the  clear,  are  from 
0.9  to  1  metre  in  width  and  length.  The  muffles 
themselves  are  from  0.55  to  0.60  metre  wide,  and  from 
O.oO  to  0.37  metre  high.  In  order  to  save  fuel,  2  or 
3  may  be  placed  in  the  same  furnace.  The  muffles 
are  constructed  of  fire  clay,  in  the  same  manner  as  the 
pots  of  glass  works.  Their  front  openings  may  be 
closed  by  cast-iron  doors  sliding  upon  rollers.  These 
doors  and  the  back  parts  of  the  muffles  have  each 
a  narrow  slit,  for  watching  the  operation  and  giving 
passage  to  the  air.  It  is  well  understood  that  the 
furnaces  are  provided  with  dampers  for  regulating 
the  draft  and  the  temperature.  The  durability  of  the 
muffles  is  increased  by  supporting  them  upon  three 
arches  or  brick  walls  resting  upon  the  bed  of  the 
furnace.  The  spaces  between  these  walls  form  flues 
from  0.20  to  0.23  metre  square.  When  the  fuel  is 
charcoal,  it  may  be  introduced  by  an  opening  on  top, 
as  in  assay  furnaces. 

"  The  conversion  of  the  sulphate  of  soda  into  sul- 
phide of  sodium  is  effected  in  a  furnace  analogous  to 
those  employed  in  the  manufacture  of  soda.  In  our 
works  I  have  replaced  the  single  lateral  fireplace  by 
two  smaller  ones,  opposite  to  each  other,  and  I  have 


BLUE  COLORS.  285 

found  by  experience  that  this  disposition  gives  a 
saving  of  time  and  labor,  especially  when  the  bed  of 
the  furnace  is  more  than  2  metres  in  length. 

"Let  us  now  pass  to  the  preparation  of  the  raw 
materials,  and  to  the  manufacture  of  ultramarine 
blue. 

"  The  dry  clay,  coarsely  broken  with  wooden  stamp- 
ers, is  placed  in  rectangular  wooden  vats,  2  metres 
long  and  1  metre  wide,  where  it  is  covered  with  water, 
and  left  to  rest  for  several  days.  The  resulting  paste 
is  then  floated,  as  in  porcelain  works,  for  separating 
the  sand  and  the  coarse  portions.  The  purified  clay, 
in  the  state  of  soft  paste,  is  kept  under  a  shed,  and 
its  yield  in  dry  clay  is  accurately  determined  each 
time  that  it  is  used  for  the  preparation  of  ultramarine. 

"The  purification  of  the  crude  sulphate  of  soda  is 
done  by  calcination  in  a  reverberatory  furnace,  by 
which  the  free  hydrochloric  acid  is  expelled.  The 
crude  salt  is  broken  into  pieces  of  about  1  cubic 
decimetre,  and  plunged  into  water  for  a  very  short 
time,  because  experience  has  proven  that  the  free  acid 
is  much  more  easily  removed  from  the  wet  than  from 
the  dry  salt.  The  furnace  is  filled  with  these  lumps, 
with  sufficient  spaces  left  for  the  free  access  of  the 
flame.  The  temperature  is  gradually  raised  to  an 
incipient  red  heat,  and  is  maintained  until  there  is  no 
free  acid  left.  The  calcined  salt  is  immediately  bro- 
ken, under  stamps  or  between  stones,  into  grains  of 
the  size  of  blasting  powder,  which  are  mixed  with 
the  charcoal  and  slaked  lime,  in  revolving  tuns. 
The  proportions  are  : — 

Sulphate  of  soda   100  parts. 

Powdered  charcoal  33 

Lime  slaked  in  the  air  10  " 


286 


MAJsTUFACTURE  OF  COLORS. 


"  The  ground  mixture  is  spread  upon  the  bed  of 
the  reverberatory  furnace,  and  covered  3  to  4  centi- 
metres deep  with  slaked  lime,  which  is  compressed 
with  a  flat  iron  shovel.  All  the  doors  of  the  furnace 
are  then  closed,  and  when  the  mass  is  thoroughly  in 
fusion,  it  is  rapidly  stirred,  and  a  few  shovelfuls  of 
charcoal  dust  are  thrown  in.  The  bath  is  left  un- 
disturbed for  some  time,  until  gas  jets  no  longer  burn 
at  the  sui-face.  The  sulphide  of  sodium  is  then  re- 
moved with  iron  ladles,  and  poured  into  shallow  cast- 
iron  moulds,  in  which  it  solidifies. 

"  The  sulphide  of  sodium  and  the  carbonate  of  soda 
thus  obtained  are  dissolved  in  boiling  water,  and  the 
liquor  is  left  to  settle,  out  of  contact  of  the  air,  in 
tubs,  in  which  it  deposits  carbonate  of  soda,  sulphate 
of  soda,  and  charcoal  in  very  minute  particles.  The 
sulphate  of  soda  is  treated  in  the  aforesaid  manner 
for  another  operation,  and  it  is  very  important  that 
all  of  the  charcoal  should  be  deposited,  because  a 
trace  of  it  is  sufficient  to  impair  the  brightness  of 
the  ultramarine.  The  clear  and  decanted  solution  is 
then  heated,  saturated  with  powdered  sulphur,  and 
concentrated  by  ebullition  until  it  contains  25  per 
cent,  of  dry  bisulphide  of  sodium,  and  marks  about 
25°  Be.  From  40  to  50  parts  of  sulphur  are  em- 
ployed for  each  100  parts  of  fused  sulphide  of 
sodium. 

"  After  the  solution  of  sulphide  of  sodium  has 
deposited  the  slight  excess  of  sulphur  contained  in 
it,  it  is  decanted  into  glass  carboys,  which  are  care- 
fully closed,  in  order  to  prevent  the  contact  of  the 
air. 

"  The  raw  materials  being  prepared,  the  prepara- 
tion of  ultramarine  is  as  follows :  50  kilogrammes  of 


BLUE  COLORS. 


287 


the  above  solution  of  sulphide  of  sodium  are  evapo- 
rated in  a  shallow  cast-iron  pan  to  a  syrupy  consist- 
ency;  then  a  quantity  of  washed  and  wet  clay,  cor- 
responding to  12.5  kilogrammes  of  dry  clay,  are 
added  to  it,  and  the  whole  is  thoroughly  mixed  with 
an  iron  spatula.  "While  the  mass  is  still  pasty  enough 
to  be  stirred,  there  is  added  to  it  a  solution  of  150 
grammes  of  sulphate  of  iron,  free  from  copper,  which 
is  also  carefully  mixed.  The  stirring  is  continued 
until  the  mixture  is  entirely  dry,  when  the  substances 
are  finely  powdered. 

"  This  powder  is  charged  into  the  muffles,  and  spread 
in  layers  6  to  8  centimetres  deep,  which  correspond 
to  a  weight  of  15  to  20  kilogrammes.  The  fire  is 
continued  for  about  one  hour  after  the  material  has  be- 
come red,  and  frequent  stirrings  are  given,  at  the 
same  time  that  the  air  is  allowed  free  access.  The 
mass  becomes  successively  colored  a  liver  color,  then 
red,  green,  and  blue.  This  operation  requires  a  great 
deal  of  attention  and  practice,  because  too  little  heat 
produces  no  ultramarine,  and  an  excess  of  tempera- 
ture impairs  the  beauty  of  the  color. 

"  The  substance  is  then  removed  from  the  muffle, 
and  purified  by  washings  with  water.  The  liquors, 
which  contain  sulphate  of  soda  and  sulphide  of  so- 
dium, are  generally  thrown  away,  but  they  might  be 
used  for  the  preparation  of  the  sulphide  of  sodium. 
The  precipitated  ultramarine  is  collected  and  drained 
in  cloth  bags,  and  then  dried  in  a  stove-room.  Its 
color  is  generally  a  dark  green  or  a  blackish-blue. 

"  The  dry  mass  is  finely  ground,  passed  through  a 
silk  sieve,  and  calcined  again  by  portions  of  5  to  7 
kilogrammes,  in  muffles  kept  specially  for  this  opera- 
tion, and  which  are  45  to  50  centimetres  wide,  and  80 


288 


MAKUFACTURE  OF  COLORS. 


to  90  centimetres  long.  A  dark  red  heat  is  sufficient 
for  this  calcination.  As  soon  as  the  blue  color  begins 
to  appear,  the  powder  is  constantly  stirred  with  an  iron 
tool,  until  the  whole  is  of  a  pure  blue.  The  operation 
lasts  from  one-half  to  three-quarters  of  an  hour,  and 
there  is  no  advantage  in  continuing  it  longer,  or  in 
having  a  more  intense  fire.  The  powder  is  removed, 
and  left  to  cool  in  the  air  upon  granite  slabs.  It 
often  happens,  but  not  always,  that  the  color  acquires, 
while  cooling,  greater  brightness  and  beauty. 

"  The  ultramarine  blue  is  afterwards  ground  under 
granite  stones,  1.5  metres  in  diameter,  then  washed 
and  floated  and  sorted,  according  to  its  degree  of 
fineness,  into  the  numbers  ^,  1,  2,  3,  4,  etc. 

"  An  excellent  method  for  ascertaining  the  quality 
of  ultramarine  blue  consists  in  heating  it  in  a  glass 
tube,  placed  upon  a  lighted  alcohol  lamp,  and  through 
which  is  passed  a  stream  of  hydrogen.  The  pigment 
will  be  the  better  and  the  more  durable,  as  its  blue 
color  is  longer  in  disappearing.  Native  ultramarine 
loses  its  color  only  after  one  or  two  hours,  or  even 
longer ;  the  best  artificial  ultramarine  of  Nuremberg 
(mark  0)  ceases  to  be  blue  after  half  an  hour,  and  the 
inferior  quality  (mark  5)  after  a  few  minutes  only." 

F.  Winter  field  Process. 

Mr.  "Winterfield  has  proposed  a  process  for  the 
manufacture  of  ultramarine  blue,  which  he  claims  to 
give  a  produce  as  fine  as  Guimet's  ultramarine,  and 
at  a  very  low  price. 

"200  parts  of  soda  ash  (from  the  evaporation  of 
the  mother-liquors  of  the  crystallized  carbonate  of 
soda)  are  dissolved  in  boiling  water,  and  there  are 
added  100  parts  of  powdered  sulphur,  4  of  sulphate  of 


BLUE  COLORS. 


289 


iron  dissolved  in  water,  and  100  parts  of  powdered 
clay.  The  whole  is  thoroughly  mixed  and  evaporated 
to  dryness.  The  dry  and  finely  powdered  mixture 
is  introduced  into  vessels  of  fire-clay,  holding  about 
4  to  5  kilogrammes,  and  which  may  be  closed  with 
a  clay  cover.  These  vessels  are  heated  in  a  furnace, 
and  their  contents  are  stirred  now  and  then  with  an 
iron  rod.  When  the  mass  begins  to  sink  down,  and 
acquires  a  blue-black  coloration,  passing  to  a  green 
when  cold,  this  operation  is  finished.  For  quantities 
of  5  kilogrammes,  about  four  hours  of  continuous 
calcination  are  necessary.  The  cooling  of  the  mass 
should  take  place  out  of  contact  with  the  air,  the 
cover  is  therefore  carefully  luted  upon  the  vessel. 
The  cold  substance  is  then  coarsely  broken,  dirty- 
looking  fragments  are  removed,  and  the  remainder  is 
washed  with  hot  water.  The  still  wet  powder  is 
finely  ground.  By  this  treatment,  and  under  the 
action  of  the  air,  the  green  color  passes  to  a  fine  blue. 
The  clay  employed  is  not  very  plastic,  and  is  quite 
free  from  iron.  Its  color,  before  calcination,  is  a 
grayish-white.  It  is  strongly  calcined,  in  order  to 
destroy  the  organic  substances  which  may  have  been 
present,  and  then  finely  ground  before  use.  The  soda 
ash  requires  also  to  be  calcined,  in  order  to  destroy 
the  organic  substances.  The  best  vessels  for  this 
operation  are  a  kind  of  fire-clay  retorts,  placed  ob- 
liquely in  the  furnace,  so  that  their  opening  is  not 
exposed  to  the  fire.  The  aperture  is  closed  with  a 
perforated  cover,  through  which  the  stirring  rod 
passes." 

G.  Bi'unner  Process, 
Mr.  C.  Brunner  has  published  in  the  TecJinologiste, 
vol.  8,  pp.  110-162,  a  very  interesting  memoir  on  the 
19 


290 


MANUFACTURE  OF  COLORS. 


manufacture  of  artificial  ultramarine,  from  which  we 
take  the  following  extracts  : — 

Before  explaining  the  process  itself,  says  he,  which 
I  have  verified  by  a  great  many  experiments,  I  shall 
make  some  remarks  on  the  choice  of  the  raw  mate- 
rials, and  he  continues : — 

1.  Silica, — I  have  used  a  gravel,  or  coarse  silicious 
sand,  found  near  Lengnau,  Canton  of  Berne.  It  is 
known  in  the  country  under  the  name  of  Hupererde^ 
and  is  employed  as  a  cement  in  the  manufacture  of 
fire-bricks,  crucibles,  and  other  articles,  which  must 
stand  a  very  high  temperature."^  I  have  always  used 
it  perfectly  ground  and  floated. 

2.  Alumina, — Instead  of  this  substance,  I  have 
employed  the  potassa  alum ;  and,  although  a  small 
proportion  of  iron  does  not  appear  disadvantageous, 
I  advise  purifying  the  alum  by  a  second  crystalliza- 
tion. I  have  heated  it  until  it  acquires  the  properties 
and  the  appearance  of  the  alumen  ustum  of  the  phar- 
macopoeia. On  a  small  scale,  this  operation  may  be 
performed  in  a  silver  dish;  but  in  manufacturing 
works  a  special  furnace  will  be  needed.  At  all  events, 
it  is  tedious  work.  The  burnt  alum  is  then  pulver- 
ized, and  a  sample  of  it  is  calcined  at  a  moderate  red 
heat  in  a  platinum  dish,  in  order  to  determine  the 
proportion  of  water  it  still  contains.    This  determi- 

*  The  analysis  of  this  sand  is  as  follows: — 


Silica 

.  94.25 

.  1.61 

100.00 

BLUE  COLORS. 


291 


nation  is  not  very  accurate,  because,  according  to  the 
degree  of  red  heat  used,  there  are  variable  proportions 
of  sulphuric  acid  disengaged  with  the  steam,  but  it  is 
sufficiently  accurate  for  practice.*  The  burnt  alum 
is  kept  in  well-closed  vessels. 

3.  Sulphur, — For  the  calcination  of  the  mixtures, 
ordinary  sublimed  sulphur  may  be  used ;  but  in  the 
last  combination  with  sulphur  it  is  better  to  purify  it 
by  distillation. 

4.  CharcoaL — The  ordinary  wood  charcoal  is  finely 
powdered. 

5.  Carhonate  of  soda. — The  crystallized  carbonate 
of  soda  is  made  to  effloresce  in  the  air  of  a  hot  room, 
and  the  resulting  powder  is  heated  in  a  dish  until  all 
the  water  disappears. 

The  preparation  of  the  ultramarine  is  made  in  the 
following  manner :  A  mixture  is  made  of — 

Silica  (huper)       .   10  parts. 

Burnt  alum  (calculated  anhydrous)      .       .  240  " 

Powdered  charcoal  48  " 

Sublimed  sulphur  ......  144  " 

Anhydrous  carbonate  of  soda       .       .       .  240  " 

In  order  to  obtain  a  thorough  mixture,  the  mate- 
rials are  first  incorporated  together  in  the  ordinary 
manner,  in  a  mortar  or  dish,  and  then  in  a  powdering 
apparatus,  made  of  a  thick  copper  flask,  tinned  inside, 
and  holding  about  2  litres.  I  put  in  from  15  to  30 
grammes  of  the  mixture,  and  from  600  to  700  grammes 
of  coarse  granules  of  cast-iron.  The  flask  is  closed, 
and  shaken  vigorously  for  eight  or  ten  minutes,  and 

*  Further  experiments  have  demonstrated  that  powdered  alum, 
dried  in  the  air,  may  be  successfully  employed ;  the  tedious  opera- 
tion of  burning  it  may  therefore  be  dispensed  with. 


292 


MANUFACTURE  OF  COLORS. 


the  contents  are  sifted  upon  a  metallic  sieve,  which 
retains  the  iron  granules. 

The  success  of  the  operation  depends  especially  on 
a  careful  and  thorough  mixture.  The  powder  must 
be  really  impalpable,  and  an  ordinary  magnifying 
glass  should  show  no  difference  of  coloration  in  the 
particles. 

A  Hessian  crucible  is  then  entirely  filled  with  this 
mixture,  and  closed  with  a  luted  cover.  The  crucible 
is  rapidly  raised  to  a  moderate  red  heat,  which  is  main- 
tained for  one  hour  and  a  half.  The  degree  of  tem- 
perature is  important,  but,  after  a  little  practice,  it  is 
easily  learned;  at  all  events,  an  excess  of  heat  is  to  be 
avoided.  When  the  operation  is  successful  the  cold 
contents  of  the  crucible  appear  as  a  sunken  and  porous 
mass,  partly  greenish-yellow  and  partly  reddish-yel- 
low, resembling  liver  of  sulphur,  and  occupying 
about  two-fifths  of  its  former  volume.  If  it  be  hard 
and  fused,  brown,  and  of  a  still  more  reduced  volume, 
the  heat  has  been  too  great. 

The  porous  pieces  are  easily  detached  from  the 
crucible,  and  are  thrown  into  water.  The  mass 
softens,  and  there  results  a  solution  of  sulphide  of 
sodium,  and  a  greenish-blue  powder  which  precipi- 
tates. The  powder  is  washed  several  times  with 
water,  which  may  be  hot,  and  until  the  liquor  becomes 
tasteless.    The  residue  is  then  dried. 

The  washed  product  is  in  the  state  of  a  light  pow- 
,  der,  of  a  clear  ash-gray  color.  A  small  sample  is 
heated  in  a  porcelain  dish  with  a  small  quantity  of 
sulphur,  in  order  to  see  whether  the  combustion  of 
the  latter  substance  causes  it  to  assume  a  bluish  tinge. 
This  coloration  will  always  be  feeble,  about  like  that 
of  blued  linens. 


BLUE  COLORS. 


293 


This  product  is  then  intimately  mixed  with  an 
equal  weight  of  snlphiir,  and  one-and-a-half  times  its 
weight  of  anhydrous  carbonate  of  soda,  in  the  manner 
already  explained.  Another  calcination  is  made  at 
the  same  temperature,  and  the  volume  of  the  mass 
diminishes  again,  but  less  than  formerly.  After  cool- 
ing, the  contents  of  the  crucible  are  washed  in  water, 
and  the  residue  is  dried. 

This  new  product,  calcined  with  sulphur  in  a  por- 
celain dish,  should,  this  time,  acquire  a  more  intense 
bluish  hue. 

The  amount  of  washed  substance  is  about  the  same 
as  after  the  first  calcination.  A  third  calcination 
with  sulphur  and  carbonate  of  soda,  in  the  proportions 
previously  stated,  is  followed  by  a  more  thorough 
washing.  It  is  even  useful  to  boil  the  product  in 
water,  and  to  finish  the  washing  upon  a  filter,  until 
the  liquors  are  no  longer  colored  black  by  the  acetate 
of  lead.  The  future  color  of  the  product  depends 
partly  upon  the  fulfilment  of  these  precautions. 

Another  test  with  burning  sulphur  is  made  to  see 
whether  a  fine  blue  color  will  appear.  If  it  be  satis- 
factory, the  product  passes  to  the  finishing  operation  ; 
in  the  contrary  case,  it  is  again  calcined  with  sulphur 
and  carbonate  of  soda.  Ordinarily,  three  calcinations 
are  sufficient ;  but,  if  they  have  been  eflected  at  too 
low  a  temperature,  a  fourth  calcination  is  necessary. 

The  dry  and  bluish-green  powder  is  passed  through 
a  gauze  sieve,  in  order  to  separate  a  few  hard  brown 
granules,  which  come  from  the  crucible  or  from  the 
compound  itself  fused  at  certain  points. 

The  last  operation,  that  is,  a  combustion  with  sul- 
phur, is  made  upon  a  plate  of  cast-iron,  on  the  surface 
of  which  there  is  spread  a  layer,  two  to  three  milli- 


294 


MA^5"UrACTUBE  OF  COLORS. 


metres  thick,  of  pure  powdered  sulphur.  An  equal 
quantity,  or  a  little  more,  of  the  dry  powdered  pro- 
duct is  dusted  over  the  sulphur  by  means  of  a  sieve. 
The  cast-iron  plate  is  heated  upon  a  charcoal  fire 
until  the  sulphur  becomes  inflamed,  and  the  tempera- 
ture should  be  such  that  all  the  sulphur  will  burn 
out  without  the  product  being  too  much  calcined. 
It  is  sometimes  necessary  to  remove  the  charcoal  fire. 
On  a  large  scale,  this  combustion  should  be  effected 
in  furnaces  provided  with  doors  for  regulating  the 
access  of  the  air,  and,  therefore,  the  intensity  of  the 
combustion.  This  operation  is  repeated  three  and 
even  four  times  with  the  same  powder,  which,  after 
each  combustion,  is  removed  from  the  plate  and 
ground.  When  the  product  has  attained  its  greatest 
intensity  of  coloration,  the  whole  operation  is  finished. 
In  the  manufacture  of  large  quantities,  it  will  be  well 
to  base  the  mode  of  working  upon  experiments  made 
on  small  samples,  which  are  mixed  with  half  of  their 
weight  of  sulphur,  and  spread  upon  a  cast-iron  plate. 

This  last  operation  somewhat  diminishes  the  volume 
of  the  product,  and  imparts  to  it  a  porous  and  flaky 
appearance.  I  have  been  unable,  with  a  magnifier, 
to  discover  any  sign  of  crystallization.  For  its  em- 
ployment, the  product  requires  to  be  ground  again 
finely.  The  yield  in  finished  product  is  about  one 
hundred  and  sixty  parts  of  the  materials  previously 
indicated. 

Before  finishing,  I  shall  point  out  several  experi- 
ments, which,  in  my  opinion,  throw  some  light  upon 
the  origin,  the  formation,  and  the  chemical  composi- 
tion'of  artificial  ultramarine. 

During  the  first  calcination  of  the  mixture,  there  is 
already  formed  a  chemical  compound  of  sulphur, 


BLUE  COLORS. 


295 


sodium,  silica,  and  alumina.  This  compound  is  now 
but  slightly  colored,  and  sometimes  not  at  all.  That 
there  is  a  combination  is  proven  by  the  fact  that  the 
well-washed  powder  is  decomposed  by  acids  ;  sulphu- 
retted hydrogen  is  disengaged,  and  gelatinous  silica 
is  precipitated.  The  addition  of  powdered  charcoal 
to  the  mass,  during  this  first  calcination,  is  not  abso- 
lutely necessary,  but  it  prevents  the  fusion  of  the 
mass.  Such  addition  is  useless  for  the  other  calcina- 
tions. 

During  the  second  calcination  with  sulphur  and 
carbonate  of  soda,  the  proportion  of  sulphur,  and 
possibly  of  sodium,  increases,  although  the  weight  of 
the  product  is  not  much  greater.  The  increase  in  the 
proportion  is  certainly  not  considerable,  and  is  coun- 
terbalanced in  part  by  the  losses  of  manipulation. 

In  this  state,  the  washed  and  dried  product,  although 
but  slightly  colored,  possesses  a  real  bluish-green  hue, 
which,  after  combustion  Avith  sulphur  in  the  open  air, 
passes  to  a  pure  but  pale  blue. 

In  the  next  operation,  that  is,  a  third  calcination 
with  sulphur  and  carbonate  of  soda,  the  proportion  of 
sulphur  still  increases.  The  washed  and  dried  pro- 
duct is  of  an  intense  blue  color  with  a  green  reflex, 
and  is  finished,  although  it  is  yet  wanting  in  the 
remarkable  brilliancy  possessed  by  ultramarine. 

Some  persons  may  think  that  these  three  operations 
may  be  united  in  one,  whether  by  calcining  longer,  or 
by  increasing  the  proportion  of  the  materials  ;  but 
direct  experiments  made  in  that  direction  have  not 
furnished  satisfactory  results. 

The  subsequent  combustion  with  sulphur  is,  theo- 
retically speaking,  the  most  remarkable  part  of  the 
whole  operation.    The  product  acquires  by  this  treat- 


296 


MANUFACTURE  OF  COLORS. 


ment  its  real  coloration,  and  it  increases  in  weight  from 
10  to  20  per  cent.  This  increase  is  variable,  and 
depends  partly  on  the  quality  of  the  product  before 
the  combustion,  and  partly  on  the  manner  in  which 
this  combustion  is  conducted. 

It  may  seem  difficult  to  arrive  constantly,  by  three 
calcinations,  at  precisely  the  same  degree  of  color  and 
quality;  but  in  practice,  when  large  amounts  of  mate- 
rials are  worked  at  a  time,  a  greater  regularity  is  ob- 
tained. I  insist  upon  the  point,  that  a  great  degree 
of  comminution  and  a  perfect  mixture  of  the  mate- 
rials, produce  a  great  yield.  Indeed,  if  we  neglect 
these  precautions,  the  product  will  be  filled  with  a 
quantity  of  whitish  specks,  and  will  never  acquire  a 
fine  color;  it  may  even  acquire  a  brownish  hue. 
During  the  combustion  with  sulphur,  the  powder  in- 
creases in  weight.  This  increase  is  not  always  con- 
stant, and  may,  by  combustions  repeated  ten  and  even 
fifteen  times,  amount  to  20  per  cent.  After  three  or 
four  successive  combustions,  the  color  has  acquired 
its  greatest  intensity,  and  the  increase  of  weight  may 
be  5  to  10  per  cent.* 

In  order  to  compare  the  increase  of  weight  with 
the  proportion  of  sulphur,  I  have  determined  this  in 
samples  of  the  mixture  before  the  calcination,  and 
after  each  heat. 

The  following  analysis  gives  the  centesimal  com- 
position of  the  ultramarine  which  has  not  been 
burned  with  sulphur : — 

*  Clement  and  Desormes  had  already  published  the  fact,  that 
real  ultramarine  increases  in  weight  about  1  per  cent.,  when  it  is 
heated  in  oxygen. 


BLUE  COLORS. 


297 


Silica   35.841 

Alumina                                                   .  27.821 

Lime    .       .       ...       ...  2.619 

Oxide  of  iron   2.475 

Sodium        .       .       .       .       .       .       .  18.629 

Sulphur   5.193 

Oxygen  (calculated  from  loss)     .       .       .  7.422 


And  as  100  parts,  after  the  combustion  with  sul- 
phur, become  110.16,  holding  12.811  of  sulphur,  while 
the  other  substances  are  not  changed,  it  results  that 
ultramarine  burned  with  sulphur  should  be  composed 


of— 

Silica   32.544 

Alumina   25.225 

Lime   2.377 

Oxide  of  iron       ....       .       .  2.246 

Sodium   16.910 

Sulphur   11.639 

Oxygen  (calculated  from  loss)     .       .       .  9.039 


If  now  we  distribute  the  oxygen  between  the  sul- 
phur and  the  sodium,  on  the  supposition  that  they 
form  sulphate  of  soda,  we  have,  instead  of  the  last 
three  elements : — 

Sulphate  of  soda  .    20.157  ^ 

Sodium        .       .    10.337  I  =  17.421  sulphide  of  sodium. 
Sulphur        .       .      8.084  ) 

We  see,  therefore,  that  the  sulphide  of  sodium  is 
in  the  monosulphide  state,  since  theory  requires 
10.337  of  sodium  and  7.149  of  sulphur. 

It  is  evident  that  this  mode  of  representation,  like 
those  used  for  complicated  compounds,  cannot  be  ab- 
solute, and  presents  only  a  theoretical  interest.  Sul- 
phur may  be  combined  with  the  sodium,  calcium,  and 
iron;  in  which  case  a  part  of  the  sodium  should  be 


298 


MANUFACTURE  OF  COLORS. 


calculated  as  soda.  But  these  speculations  cannot 
be  verified  by  analysis. 

If,  after  ultramarine  has  reached  the  greatest  color- 
ing intensity  by  its  combustion  with  sulphur,  this 
treatment  be  continued,  there  comes  a  time  when  the 
product  no  longer  increases  in  weight.  If  it  be  heated 
without  sulphur,  its  weight  diminishes,  and  its  blue 
color  becomes  lighter,  resembling  that  of  certain  kinds 
of  native  ultramarine,  and  it  often  acquires  a  slightly 
lilac  hue.  Besides  these  chemical  changes,  there  is 
also  another  mechanical  transformation  ;  the  powder 
ceases  to  be  light  and  flaky,  and  becomes  dense  and 
granular.  Mr.  Brunner,  however,  has  not  always 
succeeded  in  producing  this  change.  In  many  sam- 
ples found  in  the  market  this  phenomenon  is  easily 
produced ;  in  others,  it  is  less  apparent,  even  after 
heating  for  hours  together.  An  ultramarine  modified 
in  this  manner  and  treated  by  hydrochloric  acid,  does 
not  disengage  hydrosulphuric  acid,  and  contains, 
therefore,  no  unoxidized  metallic  sulphide.  It  may 
be  thought  that  there  should  be  an  increase  of  weight 
resulting  from  oxidization;  but  the  diminution  in 
weight  may  possibly  be  explained  by  supposing  that, 
while  part  of  the  sulphur  of  the  sulphide  of  sodium 
burns,  the  resulting  soda  combines  with  the  silica  or 
other  elements  of  the  compound.  Since  the  volatil- 
ized sulphur  possesses  a  greater  weight  than  the 
oxygen  which  takes  its  place,  there  must  result  a 
lesser  yield. 

These  pale  ultramarines,  at  all  events,  may  be  use- 
fully applied  in  the  arts,  and  it  is  likely  that  some 
may  be  found  among  the  manufactured  products. 

There  are  still  three  j^oints  to  be  decided  : — 


BLUE  COLORS. 


299 


"1.  How  far  necessary  is  the  proportion  of  lime 
found  in  nearly  all  commercial  ultramarine  blues  ? 

"  2.  Is  the  presence  of  iron  useful,  or  unfavorable, 
to  the  production  of  the  color  ? 

''3.  Is  soda  absolutely  necessary,  or  is  it  not  pos- 
sible to  replace  it  by  potassa? 

"  The  presence  of  lime  is  not  absolutely  necessary, 
and  this  is  proven  by  the  small  proportion  of  it  in  the 
indicated  mixtures.  Moreover,  I  have  checked  the 
exactness  of  this  conclusion  by  direct  experiments, 
in  which  I  have  added  as  much  as  8  per  cent,  of  lime 
in  certain  mixtures.  There  was  no  difference  what- 
ever between  the  products  obtained  and  those  made 
without  lime. 

"  Iron  is  neither  important  nor  absolutely  neces- 
sary. Indeed,  a  mixture  made  according  to  the  pre- 
ceding formula,  but  with  materials  free  from  iron,^ 
and  without  using  iron  granules  during  the  pulveri- 
zation, has  given  a  product  entirely  similar  to  that 
prepared  in  the  ordinary  manner.  However,  the  fine 
artificial  ultramarine  of  Guimet,  and  the  native  one 
imported  from  Rome,  show  the  presence  of  iron  by 
delicate  analytical  tests. 

"  It  does  not  seem  important  to  me  to  investigate 
whether  a  large  proportion  of  iron  is  to  be  avoided  in 
the  color;  but,  a  priori^  it  seems  that  it  should  be  so. 

"Lastly,  a  question  which  appears  to  me  very  in- 
teresting is,  whether  the  blue  coloration  is  principally 
due  to  a  sodium  comj)ound,  or  if  it  cannot  be  pro- 
duced with  potassa. 

*  The  silica  was  prepared  by  calcining  the  huper  with  the  car- 
bonates of  soda  and  potassa,  filtering,  and  precipitating  the  silica 
with  hydrochloric  acid.  The  iron  in  the  charcoal  has  not  been 
considered. 


\ 


300  MANUFACTURE  OF  COLORS. 

"  I  have,  therefore,  conducted  an  operation  accord- 
ing to  the  preceding  formula,  with  the  exception  that 
the  carbonate  of  soda  was  replaced  by  carbonate  of 
potassa,  prepared  from  the  combustion  of  cream  of 
tartar.  After  three  calcinations  of  the  mixture  there 
was  obtained  a  white  mass,  which,  being  burned  with 
sulphur,  did  not  acquire  any  blue  coloration,  although 
it  disengaged  an  abundance  of  sulphuretted  hydrogen 
by  a  treatment  with  hydrochloric  acid. 

"  It  is  then  demonstrated,  in  conformity  with  the 
assertion  of  Gmelin,  that  potassa  (without  soda)  does 
not  produce  a  blue  ultramarine,  but  that  a  similar 
colorless  compound  is  obtained.  This  experiment 
seems  to  be  a  further  proof  that  the  blue  color  is  not 
due  to  the  presence  of  iron."* 

H.  Dippel  Process. 

In  a  pamphlet  published  by  Mr.  J.  P.  Dippel,  of 
Cassel,  on  the  preparation  of  artificial  ultramarine, 
this  chemist  recommends  the  following  process  as 
having  been  for  a  long  time  advantageously  practised 
in  manufactories. 

The  materials  are  clay,  Glauber  salt  (sulphate  of 
soda)  with  an  excess  of  sulphuric  acid,  bituminous 
coal,  and  sulphur ;  each  of  which  should  possess  cer- 
tain qualities.    The  first  three  are  mixed  in  certain 

*  I  had  already  written  the  above  memoir  when  one  of  Mr.  C. 
P.  Pruckner,  upon  the  manufacture  of  ultramarine,  fell  into  my 
hands.  Time  and  circumstances  prevented  me  from  experiment- 
ing with  his  mode  of  preparation,  which  resembles  that  of  Gmelin, 
and  to  compare  it  with  mine.  It  seems,  however,  possible  to 
arrive  at  the  same  results  in  different  ways,  although  I  differ  from 
the  opinion  of  Mr.  Pruckner,  who  believes  that  the  presence  of 
iron  is  absolutely  necessary. 


BLUE  COLORS. 


301 


proportions,  and  then  brought  to  a  red  heat  in  a  cru- 
cible. After  cooling,  the  mass  is  removed  from  the 
crucible  and  then  calcined  again  in  a  tube,  with  the 
access  of  the  air.  The  product  is  afterwards  steeped 
in  water,  ground  wet,  and  lastly  heated  to  produce 
the  blue  color  in  the  following  manner :  the  powder 
is  mixed  with  sulphur,  and  heated  in  the  presence  of 
just  enough  air  to  cause  an  incomplete  oxidization  of 
the  sulphur.  When  the  fine  blue  color  has  been  de- 
veloped the  pigment  is  ground  again,  then  floated  and 
dried. 

J.  Habich  Process. 

Mr.  G.  C.  Habich  has  published  in  the  Technologiste, 
vol.  xvii.  p.  411,  the  following  remarks  on  ultramarine 
and  its  manufacture  : — 

"Two  kinds  of  ultramarine  blue  may  be  distin- 
guished from  their  behavior  in  presence  of  concen- 
trated acids.  When  cold  hydrochloric  acid  is  poured 
upon  ultramarine,  the  color  disappears,  part  of  the 
sulphur  is  disengaged  as  hydrosulphuric  acid,  and  the 
other  part  settles  with  the  remainder  of  the  powder. 
It  is  then  that  there  appears  a  characteristic  difference 
due  to  the  modes  of  preparation.  When  ultramarine 
has  been  manufactured  from  artificial  aluminous  sili- 
cates, gelatinous  silica  is  precipitated.  On  the  con- 
trary, when  white  clay  has  been  used,  there  is  no  pro- 
duction of  gelatinous  silica. 

When  the  manufacture  of  ultramarine  took  a 
foothold  in  Germany,  the  first  named  process  was  em- 
ployed ;  and  although  it  is  too  expensive,  it  never- 
theless presents  a  real  scientific  interest. 

"  Soda,  white  sand,  sulphur,  and  powdered  bitu- 
minous coal  were  melted  together,  and  the  resulting 


302 


MANUFACTURE  OF  COLORS. 


mass  being  dissolved  in  water,  gave  a  solution  of 
polysiilphide  of  sodium  and  of  silicate  of  soda,  with 
which  another  hot  solution  of  alum  was  precipitated. 
The  result  of  the  decomposition  was  an  abundant 
production  of  sulphuretted  hydrogen,  and  a  precipi- 
tate of  silicate  of  alumina  and  of  sulphur.  This  pre- 
cipitate was  washed,  dried,  and  introduced  into  a 
boiling  bath  of  soda  and  sulphur.  The  molten  mass, 
when  the  operation  was  successful,  crumbled  in  hot 
water,  and  deposited  a  very  finely  comminuted  pow- 
der of  a  bluish-green  color,  called  green  ultramarine, 
which,  being  entirely  deprived  of  soluble  salts  by  a 
careful  washing,  was  dried.  This  green  ultramarine 
was  then  rendered  blue  by  a  calcination  with  sub- 
limed sulphur,  as  we  shall  see  further  on. 

"We  see  that  this  process,  on  account  of  the  mate- 
rials employed,  was  very  expensive.  On  the  other 
hand,  we  must  acknowledge  that  the  purity  of  color 
of  the  product  was  far  superior  to  that  of  the  ultra- 
marines prepared  with  clay  by  the  present  process. 

"  This  last  process  is  more  economical,  and  its  mode 
of  operation  varies  with  diflPerent  manufactures.  I 
shall  explain  that  which  I  found  to  succeed  the  best. 

''Preference  is  given  to  that  kind  of  white  clay 
which  is  found  in  various  localities,  near  Worms  for 
instance,  and  which  is  called  lenzine  (lenzinite).  It 
is  thoroughly  deprived,  by  floating,  of  all  the  sandy 
parts  which  may  be  mixed  with  it,  then  dried  and 
finely  powdered.  10  parts  (in  weight)  of  this  powder 
are  mixed  with  22  parts  of  Glauber  salt  (anhydrous 
and  free  from  iron),  3  of  sublimed  sulphur,  and  3.5 
parts  of  colophony. 

"  This  mixture  is  charged  into  pots,  made  of  a  scarcely 
plastic  clay,  to  which  a  certain  proportion  of  sand  is 


BLUE  COLORS. 


303 


sometimes  added.  These  vessels  are  made  upon  a 
potter's  wheel,  and,  after  a  protracted  desiccation,  they 
are  burned.  Their  shape  is  conical,  thirty  centime- 
tres in  diameter  at  the  bottom,  and  of  an  equal  height. 
The  aperture  of  each,  after  the  charge  is  put  in,  is 
closed  with  a  cover,  which  is  luted  on  with  clay.  The 
mixture  should  be  strongly  compressed. 

"  The  pots  are  then  placed  in  the  same  oven  in 
which  are  burned  the  empty  ones ;  but  as  the  latter 
do  not  require  as  uniform  a  temperature  as  the  former, 
they  are  put  near  the  fireplace  and  near  the  chimney 
flue,  while  the  central  part  of  the  oven  is  reserved  for 
the  filled  pots. 

"A  heat  in  these  furnaces  lasts  three  days,  and 
the  fire  should  be  maintained  until  the  mass  in  the 
pots  has  sunk  and  has  become  agglutinated.  After 
cooling  in  the  furnace,  the  pots  are  broken,  and  the 
surface  of  the  calcined  mass  is  cleaned  of  any  extra- 
neous matter,  which  generally  comes  from  the  pots 
themselves.  It  is  then  coarsely  ground,  and  calcined 
in  a  reverberatory  furnace  or  in  a  cast-iron  dish,  as 
long  as  sulphur  vapors  are  disengaged. 

"  This  calcined  mass  is  lixiviated  with  water,  until 
most  of  the  soluble  salts  are  removed.  The  liquors 
are  evaporated  to  dryness,  and  give  Glauber  salt. 

"  The  washed  bluish-green  powder  is  ground  again 
to  a  fine  magma,  under  hard  quartz  stones,  because 
soft  stones  become  impregnated  with  the  material, 
and  crumble  easily. 

"  The  schlamm  or  colored  magma  is  floated  (levi- 
gated) in  a  special  apparatus,  which  gives  on  one 
side  a  highly  comminuted  powder,  and  on  the  other 
a  coarse  article  which  is  ground  again. 

"  This  levigated  powder  is  thoroughly  washed  with 


304 


MANUrACTURE  OF  COLORS. 


water,  until  a  sample  ceases  to  be  improved  by  the 
operation,  or  until  two  samples  from  two  consecutive 
washings  have  exactly  the  same  coloration.  The 
pigment  is  then  collected  upon  a  filter,  drained  and 
dried.    It  has  a  pure,  but  pale  bluish-green  hue. 

"  The  operation  by  which  the  blue  color  is  made  to 
appear  is  conducted  in  a  horizontal  cast-iron  cylinder, 
placed  above  a  fireplace  and  covered  with  brickwork. 
On  the  top  of  the  cylinder  there  are  several  openings 
for  charging  the  sulphur  and  allowing  the  access  of 
the  air.  These  apertures  may  be  closed  when  desired. 
This  cylinder  also  contains  a  stirring  apparatus,  the 
blades  of  which  come  very  near  to  the  bottom. 

"This  apparatus  is  about  one-half  filled  with  the 
powder,  which  has  been  passed  through  a  fine  hair 
sieve.  The  fire  is  then  urged  until  all  the  material 
becomes  red  hot.  For  every  100  parts  of  sifted  pow- 
der introduced  into  the  cylinder,  6  parts  of  sublimed 
sulphur  are  thrown  in  through  the  apertures.  As 
soon  as  the  sulphur  has  caught  fire  the  fire  is  removed, 
and  the  stirring  apparatus  is  set  in  motion.  A  little 
while  after,  fresh  fire  is  put  upon  the  grate  bars,  and 
3  per  cent,  more  of  sulphur  is  added.  A  moderate 
heat  is  continued,  the  mass  is  constantly  stirred,  and 
air  is  largely  admitted,  until  the  color  has  acquired 
its  greatest  intensity. 

"  When  this  color  is  left  exposed  for  a  long  time  to 
moist  air,  it  may  happen  that  it  will  agglomerate  and 
form  hard  lumps.  It  is  a  proof  that  it  still  retains 
soluble  salts,  and  that  it  has  not  been  sufficiently 
washed." 

K.  Gentele  Processes. 

Mr.  J.  G.  Gentele,  a  learned  manufacturer,  has 
published  a  very  interesting  memoir  on  the  prepara- 


BLUE  COLOTIS. 


305 


tioii  of  artificial  ultramarine.  We  borrow  from  the 
Technologiste,  vol.  xviii.  pp.  389-411,  several  extracts 
from  this  memoir. 

"The  preparation  of  artificial  ultramarine  blue  is 
described  in  all  the  works  on  chemistry,  but  in  a 
summary  way,  and  without  sufficient  details  for 
manufacturers.  This  manufacture,  which  was  al- 
al ready  important  in  respect  to  painting,  has  still 
gained  in  interest,  since  ultramarine  has  been  suc- 
cessfully used  for  calico  printing.  This  has  deter- 
mined us  to  lay  before  the  public  all  the  practical 
data  which  we  have  been  enabled  to  collect  in  our 
own  practice,  or  from  the  French  and  German  works 
which  we  have  visited. 

"  The  manufacture  of  artificial  ultramarine  is  di- 
vided into  two  distinct  operations — first,  the  prepara- 
tion of  the  green  ultramarine  ;  second,  the  transforma- 
tion of  the  latter  into  ultramarine  blue.  The  beauty 
of  the  final  product  depends  on  the  quality  of  the 
former,  and,  therefore,  the  first  operation  requires  all 
the  attention  of  the  manufacturer.  I  shall  describe 
separately  the  preparation  of  each  of  these  products. 

1.  Manufacture  of  Ultramarine  Green. 

''Raw  materials. — The  following  substances  are 
used,  at  the  present  time,  for  the  preparation  of  ultra- 
marine green: — 

1.  Aluminous  silicate,  kaolin  for  instance. 

2.  Anhydrous  sulphate  of  soda,    )         , .       -  ^ 

^    ,   r  ^  \  n      \    i  sometimes  in  solution. 

3.  Anhydrous  carbonate  of  soda,i 

4.  Sulphide  of  sodium,  as  a  secondary  product  of  the  manu- 
facture. 

5.  Sulphur. 

6.  Wood  charcoal,  or  bituminous  coal. 

20 


306 


MANUFACTURE  OF  COLORS. 


"All  of  these  materials  require  to  be  carefully 
chosen,  and  to  be  submitted  to  certain  preparatory 
operations.  These  operations  generally  require  me- 
chanical appliances,  which  form  the  heaviest  outlay 
in  the  building  of  the  works. 

"The  most  advantageous  aluminous  silicate  is  por- 
celain clay,  or  kaolin,  or  a  white  clay,  the  composition 
of  which  should  not  be  very  different  from  that  of 
kaolin.  A  small  proportion  of  magnesia  and  lime  is 
not  objectionable;  but  a  clay,  holding  more  than  1 
per  cent,  of  oxide  of  iron,  should  be  admitted  only 
after  previous  experiments.  Kaolins  present  all  the 
desired  qualities,  and  are  not  scarce,  and  French  and 
German  manufacturers  have  no  difficulty  in  getting 
what  they  need.  Formerly,  ordinary  clays  were 
worked  with  an  addition  of  alumina,  artificially  pre- 
pared; silica  was  also  added  to  clays.  At  the  present 
time  all  these  costly  additions  are  dispensed  with  by 
a  judicious  choice  of  clays,  which,  after  calcination, 
should  have  a  composition  corresponding  approxi- 
mately to  the  formula  APO^,2SiO\  ISTo  account  is 
taken  of  small  proportions  of  lime,  magnesia,  and 
oxide  of  iron,  and  it  matters  not  whether  the  silica  is 
or  is  not  entirely  in  chemical  combination.  It  often 
occurs  that  clays  in  their  natural  state  do  not  pre- 
sent the  desired  composition,  from  being  mixed  with 
sand  and  other  mineral  substances.  But,  as  the  me- 
chanical operations  to  which  the  clays  are  submitted 
retain  most  of  these  foreign  materials,  it  results  that 
clays  so  treated  are  very  near  the  indicated  compo- 
sition. 

"  The  preparatory  working  of  the  clay,  in  order  to 
remove  its  mechanical  impurities,  is  effected  in  ex- 
actly the  same  manner  as  in  porcelain  works,  that  is. 


BLUE  COLORS. 


307 


by  levigation  or  floating.  The  washed  clay  is  dried, 
slightly  calcined,  and  then  immediately  ground  to  a 
fine  powder.  There  are,  however,  manufacturers  who 
do  not  calcine  or  grind  it. 

"The  floating  of  the  clay  is  done  either  by  hand  or 
by  power.  "When  the  clay  is  slow  to  soften  in  water 
it  is  coarsely  ground  between  two  stones,  and  then 
made  into  a  thin  paste,  which  is  allowed  to  deposit 
its  coarsest  impurities.  The  pure  clay  is  stirred  again 
in  water,  and  the  light  particles  settle  in  other  tanks. 
After  decanting  the  water,  the  pasty  mass  is  collected 
and  pressed  in  sacks,  and  dried  by  heat,  or  in  the  air 
upon  porous  slabs  of  plaster  of  Paris.  When  pure 
and  washed  kaolin  is  bought,  it  is  evident  that  these 
manipulations  are  dispensed  with. 

"  The  slight  calcination  given  to  clay  is  effected  in 
an  ordinary  reverberatory  furnace,  at  a  temperature 
not  above  the  beginning  of  a  cherry-red  heat.  By 
this  operation  the  earth  loses  all  its  combined  water, 
becomes  friable,  and  ceases  to  be  plastic ;  in  fact,  it 
can  easily  be  powdered,  which  is  the  intent  of  this 
calcination. 

"  The  clay  is  pulverized  under  stamps,  or  under  a 
vertical  stone  revolving  upon  a  horizontal  one,  and  is 
then  passed  through  a  series  of  fine  metallic  sieves. 
The  coarse  portions  are  ground  again. 

"If  the  sulphate  of  soda  be  employed  in  the  anhy- 
drous state  its  quality  should  be  considered.  It  should 
not  contain  free  acid,  and  if  it  be  sold  by  the  soda 
manufacturers,  free  from  iron  and  lead,  so  much  the 
better.  When  such  a  salt  cannot  be  had,  a  Glauber 
salt  is  bought  which  contains  no  free  hydrochloric 
acid.  It  is  dissolved  in  water,  and  the  excess  of  sul- 
phuric acid  is  saturated  with  a  small  quantity  of  milk 


308 


MANUFACTURE  OF  COLORS. 


of  lime,  which  at  the  same  time  precipitates  the  oxide 
of  iron.  The  clear  liquor  is  decanted  and  made  to 
crystallize.  The  sulphate  of  lime  and  the  excess  of 
lime  remain  in  the  deposit.  The  crystallized  sulphate 
of  soda  is  slowly  dried  in  a  cast-iron  kettle,  or,  what 
is  better,  upon  slabs  of  fire-clay  on  the  bed  of  a 
reverberatory  furnace.  In  either  case  the  product  is 
an  anhydrous  Glauber  salt  (sulphate  of  soda).  The 
clear  liquors  may  also  be  directly  evaporated,  without 
being  made  to  crystallize,  in  a  pan  which  is  always 
kept  full  of  fresh  liquor.  At  a  certain  degree  of  con- 
centration an  anhydrous  sulphate  is  precipitated, 
which  is  fished  (removed)  with  perforated  ladles. 
This  salt  is  deprived  of  all  adhering  water  by  a 
slight  calcination  in  the  reverberatory  furnace. 

"The  Glauber  salt,  either  bought  anhydrous  or 
rendered  so  by  the  above  process,  is  ground  and  passed 
through  sieves,  which  should  not  be  too  fine.  The 
ground  salt  should  be  kept  in  closed  vessels,  because 
it  may  become  compact  by  attracting  atmospheric 
moisture.  This  salt  may  be  bought  of  manufacturers 
who  evaporate  pure  liquors  and  calcine  the  residue 
afterwards  ;  but  it  is  difficult  in  ultramarine  works  to 
dispense  with  the  necessary  apparatus  for  this  treat- 
ment, because,  during  the  course  of  the  operations, 
there  are  produced  washing  liquors  containing  sul- 
phate of  soda,  which  ought  to  be  evaporated.  The 
salt,  thus  prepared,  always  contains  small  proportions 
of  chloride  of  sodium  and  of  sulphate  of  lime,  which 
form  no  impediment  to  the  manufacture. 

"  The  carbonate  of  soda  is  also  used  in  the  anhy- 
drous state,  and  it  can  be  bought  as  pure  and  as  dry 
as  desired.  The  dry  carbonate  of  soda  (soda  ash)  of 
the  manufacturers  is  the  salt  precipitated  during  the 


BLUE  COLORS. 


309 


evaporation  of  the  liquors  of  crude  soda,  and  calcined 
afterwards.  A  small  quantity  of  sulphate  of  soda  in 
it  presents  no  inconvenience.  This  carbonate  of  soda 
is  powdered  like  the  sulphate,  and  is  kept  in  the 
same  manner. 

"The  ultramarine  works  which  do  not  use  directly 
the  sulphide  of  sodium  in  solution,  should  be  provided 
with  a  certain  number  of  evaporating  kettles,  made 
of  wrought  or  cast  iron,  and  heated  by  the  waste  heat 
of  the  calcining  and  evaporating  furnaces.  The 
liquors  are  evtvporated  to  dryness,  and  are  constantly 
stirred  towards  the  end  of  the  operation.  The  sul- 
phide of  sodium  is  powdered,  and  kept,  in  the  same 
manner  as  the  sulphate  and  carbonate  of  soda.  In 
making  the  mixtures  this  sulphide  of  sodium  is 
reckoned  as  a  simple  sulphide. 

"  The  sulphur  employed  is  in  refined  rolls.  It  is 
also  ground  and  passed  through  a  fine  sieve. 

"  The  carhon  necessary  in  the  manufacture  of  ultra- 
marine may  be  derived  from  bituminous  coal,  or 
from  the  charcoal  of  any  kind  of  wood.  The  impuri- 
ties of  the  large  pieces  of  charcoal  are  removed  by 
sifting,  and  those  of  the  small  fragments  by  a  leviga- 
tion.  The  impurities,  which  are  heavier,  fall  to  the 
bottom  of  the  tank,  and  the  floating  charcoal  is  re- 
moved and  dried.  The  more  caking  kinds  of  bitu- 
minous coal  are  preferred,  provided  their  percentage 
of  ashes  is  small. 

"The  two  kinds  of  coal  are  always  reduced  to  a 
very  fine  powder  either  by  trituration  with  common 
balls  in  a  revolving  cylinder,  as  is  done  for  cannon 
powder;  or  by  grinding  with  water  in  sand-stone 
or  granite  mills,  until  the  coal  or  charcoal  forms 
an  impalpable  powder,  easily  separated   from  the 


310 


MANUFACTURE  OF  COLORS. 


water.  The  settled  powder  is  collected,  drained,  and 
dried  upon  shelves.  It  is  again  ground  and  sifted 
before  use.  This  last  method  is  very  convenient  for 
either  charcoal  or  bituminous  coal. 

"  While  compounding  the  mixture,  it  is  necessary 
that  the  component  parts  should  be  in  the  correct 
proportions,  and,  also,  that  the  mixture  should  be 
thoroughly  homogeneous.  The  more  this  condition  is 
fulfilled  the  better  the  results.  When  dry  materials 
are  used  it  is  advantageous  to  weigh  small  quantities 
of  them,  and  to  mix  them  in  a  trough  with  a  spatula. 
The  mixture  is  then  passed  through  sieves  of  medium 
fineness,  stirred  again,  sifted  anew,  and  so  on,  until 
the  proper  result  is  arrived  at.  The  sifting  of  the 
mixture  of  materials  should  be  done  by  small  quanti- 
ties at  a  time,  and  no  new  material  put  upon  the 
sieve  until  it  is  entirely  empty. 

"Another  method  has  been  adopted  in  several 
factories.  Thus,  instead  of  using  the  sulphate  and  the 
carbonate  of  soda,  or  the  sulphide  of  sodium,  in  the 
dry  state,  they  measure  solutions  of  these  salts,  mark- 
ing a  certain  hydrometric  degree,  which  corresponds 
to  a  given  proportion  of  dry  salt.  The  powdered 
kaolin  is  put  into  these  solutions,  and  the  whole  is 
evaporated  to  dryness.  The  powdered  charcoal  is 
sometimes  added  to  them.  The  dried  mixture  is  then 
slightly  calcined  in  a  reverberatory  furnace,  pow- 
dered, and  rendered  homogeneous  by  consecutive  stir- 
rings and  siftings.  Lastly,  the  powdered  sulphur  is 
added  and  mixed  in  the  same  manner. 

"  The  respective  proportions  of  the  raw  materials 
vary  considerably  with  different  manufacturers,  never- 
theless care  should  be  had — 

"  1.  That  the  soda,  either  as  sulphate  or  carbonate. 


BLUE  COLORS. 


311 


be  in  sufficient  quantity  to  saturate  half  of  the  silica 
in  the  kaolin ; 

"  2.  That  the  proportions  of  sulphur  and  soda  be 
such  as  to  produce  a  bisulphide  or  a  polysulphide  of 
sodium ; 

"3.  Lastly,  that  in  the  mixture  there  remain  enough 
sulphur  and  sodium  to  form  a  mono-sulphide  of  so- 
dium, when  all  of  the  green  ultramarine,  resulting 
from  the  silica  and  alumina,  is  extracted  from  the 
mixture. 

"  The  German  manufacturers  compose  their  mix- 
tures in  a  manner  difterent  from  that  of  the  French. 
The  latter  employ  only  the  carbonate  of  soda,  while 
the  former  use  only  the  sulphate  of  soda,  or  a  mixture 
of  sulphate  and  of  carbonate.  In  either  case,  the 
results  appear  identical.  In  the  case  of  sulphate  of 
soda,  more  carbon  and  sulphur  are  employed.  With 
the  carbonate  of  soda,  no  carbon  is  required,  and  a 
great  deal  of  sulphur  is  needed.  It  appears  that  the 
German  mode  of  manufacture  is  more  economical. 

"  I  now  give  the  formulae  employed  in  factories,  and 
which  may  be  used  for  such  mixtures : — 


I- 

II. 

III. 

Kaolin,  calcuJated  dry  .    .    .  . 

100 

100 

100 

Anhydrous  sulphate  of  soda 

83  to  100 

41 

Anhydrous  carbonate  of  soda  . 

100 

41 

Coal  

It 

12 

17 

60 

13 

"During  the  course  of  manufacture,  there  is  ob- 
tained a  lye  of  sulphide  of  sodium,  and  a  portion 
of  this  salt  may  be  usefully  substituted  for  part  of 
the  sulphate  or  carbonate  of  soda.  This  sulphide  is 
introduced,  either  evaporated  and  dry,  or  in  solu- 


312 


MANUFACTURE  OF  COLORS. 


tion,  according  as  the  various  substances  are  mixed 
dry  or  wet.  In  these  solutions  of  sulphide  of  sodium, 
the  proportion  of  sodium  alone,  and  not  that  of  sul- 
phur, is  to  be  considered.  It  has  been  ascertained 
that  100  parts  of  anhydrous  carbonate  of  soda  may 
be  replaced  by  about  80  parts  of  dry  sulphide  of 
sodium;  and  100  parts  of  dry  sulphate  of  soda,  by 
about  60  parts  of  dry  sulphide. 

"  The  principal  operation  now  to  be  done  with  the 
mixture  is  its  calcination.  It  is  necessary  that  the 
mixture  should  be  brought  to  the  proper  degree  of 
high  temperature,  without  the  contact  of  the  air,  and 
that  the  heat  should  be  maintained  long  enough  to 
penetrate  the  whole  mass  as  uniformly  as  practicable. 

"  An  irregular  and  defective  calcination  never  gives 
advantageous  results  even  with  the  best  mixtures. 
In  order  to  operate  under  the  best  conditions  this 
process  employs  vessels  resembling  crucibles  or  the 
seggars  of  porcelain  works,  which  are  heated  in 
ovens  built  of  fire-clays,  and  in  the  shape  of  small 
porcelain  ovens.  There  is  a  great  waste  of  heat  in 
these  kinds  of  furnaces,  and  in  a  majority  of  ultrama- 
rine works  it  is  partly  utilized  in  evaporating  the 
mother-liquors  or  the  wet  mixtures. 

"The  crucibles  or  calcining  vessels  are  made  of 
good  fire-clay,  which  should  not  become  soft  or 
break  at  the  temperature  required  for  the  operation. 
They  may  be  formed  upon  a  potter's  wheel,  like 
flower  pots  ;  and  if  their  shape  is  that  of  seggars,  the 
diameter  is  15  or  16  centimetres,  and  the  height  from 
8  to  10.  The  top  edge  should  be  level.  Only  a  small 
number  of  flat  covers  are  needed,  because  with  the 
seggar-like  vessels  the  bottom  of  one  becomes  the 
cover  of  that  upon  which  it  rests. 


BLUE  COLORS. 


313 


"When  crucibles  are  employed,  their  shape  is 
represented  by  Fig.  52 ;  and  the  cover  is  de- 
pressed so  as  to  receive  the  bottom  of  the  next 
crucible. 

"This  last  shape  appears  to  be  the  most 
convenient,  because,  although  the  crucibles 
may  be  placed  close  to  each  other,  there  is  enough  free 
space  between  them  to  permit  the  heat  to  circulate. 
With  seggar-shaped  vessels  it  is  necessary  to  isolate 
each  column,  and  then  there  is  danger  that  it  will 
topple  over. 

"The  calcining  furnaces  are  generally  built  one 
against  the  other,  with  a  single  partition  wall.  The 
following  cuts  give  an  idea  of  the  shape  which  has 
been  found  to  be  the  best : — 


Fig.  53. 


Fiff.  54. 


Fis.  55. 


"Fig.  53  is  a  transverse  section  of  the  calcining 
furnace. 

"Fig.  54  is  a  longitudinal  section. 
"Fig.  55  is  a  horizontal  section  near  the  bed  of  the 
furnace. 

"a,  fireplace;  h,  grate;  c,  ash  pit  with  door;  d, 
door  of  the  fireplace ;  e  e  e,  flues  going  from  the  fire- 
place into  the  calcining  space  or  room. 


314 


MANUFACTURE  OF  COLORS. 


"b,  calcining  room ;  yy,  floor  or  bed  of  this  room^ 
perforated  with  the  flues  e  e  e,  which  may  be  rendered 
smaller  by  wedge  bricks  put  into  them ;  g  brick 
walls.  In  front  of  this  furnace  there  is  a  large 
charging  door  c,  which  is  closed  with  fire-bricks 
during  the  calcination.  The  floor  or  bed  of  the  fur- 
nace is  made  level  with  fire-bricks,  placed  on  top  of 
the  arch  which  covers  the  fireplace,  d  is  the  arch 
closing  the  calcining  room,  and  provided  with  four 
flues  h  for  the  escape  of  the  heated  gases,  which  are 
collected  in  the  general  flue  e,  and  go,  either  under 
the  evaporating  kettles,  or  directly  to  the  chimney. 

"In  other  factories  they  use  the  round  porcelain 
ovens  with  three  fireplaces ;  but  these  furnaces  take 
more  room,  and  the  fire  is  not  so  easily  regulated  as 
in  the  preceding  one,  with  a  single  fireplace. 

"  In  all  ultramarine  works  there  is  a  small  experi- 
mental furnace,  which  contains  from  six  to  eight 
crucibles  or  seggar  vessels.  It  is  in  it  that  the  mix- 
tures are  tried  before  they  are  prepared  on  a  large 
scale.  This  small  furnace  is  especially  useful  for 
testing  new  qualities  of  clays,  since  the  experiment 
is  much  more  rapid  than  a  chemical  analysis.  At  the 
same  time  there  is  more  certainty  that  the  results 
obtained  on  a  small  scale  will  be  reproduced  on  a  large 
one. 

"  The  composition  or  mixture  to  be  calcined  is  put 
into  the  crucibles  or  seggars  with  a  small  shovel,  and 
then  strongly  stamped  in  with  a  wooden  tool,  with- 
out, however,  breaking  the  vessels.  The  calcining 
room  is  then  filled  nearly  to  the  top  with  piles  of 
these  crucibles,  and  care  is  taken  that  the  apertures  of 
the  flues  are  left  free.  The  changing  door  is  closed 
with  firebricks  without  cement  in  the  joints  ;  but  the 


BLUE  COLOTIS. 


315 


outside  interstices  are  filled  with  a  plastering  of  sand 
and  clay.    The  firing  is  then  begun. 

"  We  understand  that  it  is  indifferent  whether  the 
furnace  be  heated  with  bituminous  coal,  wood,  or 
peat,  provided  the  fireplace  suits  these  different  fuels. 

"  The  temperature  is  slowly  raised  to  a  light  red,  or 
an  incipient  white  heat.  When  beginning  the  manu- 
facture, it  is  necessary  to  make  a  few  trials  of  heat 
in  the  experimental  furnace.  The  degree  of  heat  is 
seen  through  an  opening,  5  centimetres  in  diameter, 
left  in  the  charging  door,  and  which  is  closed  with  a 
movable  clay  plug. 

"  The  time  required  for  a  heat,  in  the  above  fur- 
naces, varies  from  seven  to  ten  hours,  with  the  indi- 
cated compositions.  The  less  the  excess  of  sulphide 
of  sodium  in  the  mixture,  after  calcination,  the  longer 
this  composition  requires  to  be  heated,  to  arrive  at  a 
given  result. 

"  When  the  calcination  is  complete,  the  furnace  is 
left  to  cool,  with  all  the  apertures  closed ;  and,  as 
soon  as  the  temperature  has  become  low  enough,  the 
crucibles  are  removed  and  a  new  charge  is  put  in. 
In  this  manner,  three  charges  per  furnace  may  be 
made  in  a  week.  The  calcined  mass  in  the  crucibles 
has  sunk  and  is  grayish,  and  often  yellowish-green. 
The  crucibles  are  immersed  into  fresh  water,  or  into 
the  washing  liquors  of  green  ultramarine,  and  the 
contents  are  dissolved.  The  separated  mass  is  then 
washed  in  appropriate  tanks,  with  several  waters,  and 
the  last  liquors,  which  are  weak,  are  reserved  for 
solutions  or  washings,  instead  of  pure  water.  The 
ultramarine  thus  obtained  is  composed  of  porous 
fragments,  large  and  small,  which  are  ground  wet  in 
mills  similar  to  those  employed  for  porcelain  compo- 


316 


MANUFACTURE  OF  COLORS. 


sitions.  The  operation  is  continued  until  a  very  great 
degree  of  comminution  is  obtained.  The  ground 
powder  is  then  washed  several  times  by  decantation 
(that  is,  by  stirring  in  water,  settling,  and  removing 
the  liquor),  and  then  collected  upon  filters  and  dried. 
When  the  substance  is  dry,  it  is  again  stamped,  and 
passed  through  fine  hair  sieves.  In  this  state,  it  may 
be  sold  as  green  ultramarine,  or  transformed  into  blue 
ultramarine. 

"  Only  a  good  quality  of  green  ultramarine  will 
permit  of  the  preparation  of  a  fine  ultramarine  blue. 
When,  after  the  proper  care  in  the  operations,  an 
inferior  product  is  obtained,  the  cause  of  such  a  result 
must  be  found  in  the  wrong  preparation  of  the  mixture, 
and,  especially,  in  too  small  an  excess  of  sulphide  of 
sodium.  The  unequal  coloring  of  a  product  should 
be  attributed  to  a  mixture  which  has  not  been  made 
sufiiciently  homogeneous.  When  the  crucibles  break, 
the  portions  of  material  adjoining  the  cracks  are 
colored  blue  by  the  action  of  the  air ;  but  this  is  no 
great  inconvenience.  Brown  specks  show  that  the 
heat  has  not  been  sufficient,  and  that  all  the  carbon 
has  not  been  burned.  These  defective  portions  should 
be  washed  and  treated  anew  like  clay. 

"If,  in  the  above  indicated  mixtures,  we  calculate 
the  results  of  the  reactions  of  their  elements,  without 
taking  into  account  the  accidental  proportions  of 
lime  and  iron,  we  find  for  the  formula  I. — 

55.55  silica      |  parts  of  anhydrous  kaolin. 

42.00  alumina  i 
Lime,  oxide  of  iron. 
43.12  soda  ) 

22.51  sulphur  f  in  100  parts  of  andydrous  sulphate  of  soda. 
33.77  oxygen  J 
17.00  carbon. 


BLUE  COLORS. 


317 


The  result  is  composed  as  follows: — 

/  X  /.K  oo   -I-    *     -PI     -  (42.00  alumina, 

(a)  67.83  silicate  oi  alumina  ■<  ' 
^  ^  (25.83  silica, 

(b)  59.63  silicate  of  soda  (29.91  silica, 
^  ^  (29.72  soda, 

since  half  of  the  silica  has  been  taken  from  the  alu- 
mina in  the  kaolin,  and  there  remain — 

(c)  19.00  sodium, 
22.55  sulphur, 

that  is  to  say,  there  remains  a  mixture  of  a  bisulphide, 
and  of  a  monosulphide  of  sodium,  in  which  the  bisul- 
phide contains  13.70  of  sodium  and  18.90  of  sulphur, 
and  the  monosulphide,  5.85  of  sodium  and  3.65  of 
sulphur. 

"  If,  from  these  elements  A,  we  deduct  those  B  of 
green  ultramarine,  as  they  result  from  my  analyses^' 
upon  143  parts  of  this  substance,  we  shall  easily 
understand  how  the  blue  color  results.  In  the  fol- 
lowing subtractions,  no  account  is  taken  of  the  small 
proportion  of  lime  and  oxide  of  iron  held  in  kaolin, 
because  these  substances  produce  no  reaction. 

Ar^O^SiO^     NaO,SiO\  NaS^.  NaS. 

A       67.83  59.63  32.60  9.00 

B       67.65  57.09  15.07 


0.18  2.54  17.53  9.00 

"  There  remains  therefore  a  notable  excess  of  mono- 
and  of  bisulphide  of  sodium,  which  is  afterwards 
washed  out. 

*  In  a  previous  memoir,  the  author  gives  analj'ses  of  10  commer- 
cial ultramarines,  blue  and  green,  and  he  infers  from  them  that  both 
green  and  blue  ultramarines  have  an  analogous  composition,  that 
is,  an  atom  (old  st3de)  of  silicate  of  alumina  united  with  an  atom 
of  silicate  of  soda  ;  without  deciding,  however,  whether  the  green 
or  blue  color  invariably  belongs  to  these  double  silicates. 


318 


MANUFACTURE  OF  COLORS. 


"  In  the  mixture  of  formula  II.  the  proportion  of 
kaolin  is  the  same  as  in  formula  I.,  and  therefore  its 
component  parts  are  the  same.  The  anhydrous  soda 
gives — 

58.64  soda,  and  there  is,  besides, 
60.00  sulphur, 
12.00  carbon. 

"  After  the  reaction,  we  have  the  same  quantity  of 
silicate  of  soda  and  of  silicate  of  alumina  as  in  the  pre- 
ceding case.  The  charcoal  is  sufficient  for  reducing 
all  the  soda ;  and  there  is  also  enough  sulphur  for 
reducing  all  the  sulphuric  acid,  and  forming  with 
sodium  59.66  parts  of  bisulphide  of  sodium.  If  we 
operate  the  subtractions  as  above,  we  have — 


APO^SiOl 

NaO,SiO^ 

NaS^. 

A 

67.83 

59.63 

59.66 

B 

67.65 

57.09 

15.07 

0.18 

2.54 

44.59 

"  There  remains,  in  this  case,  a  much  greater  ex- 
cess of  sulphide  of  sodium  than  in  the  preceding  ope- 
ration, and  it  is  evident  that  the  composition  of  the 
mixture  may  oscillate  between  more  extended  limits, 
since,  besides  the  reactions  in  different  proportions, 
there  is  formed  only  a  certain  excess  of  sulphide  of 
sodium.  However,  it  is  also  necessary  that  the  car- 
bon added  should  be  burned. 

"  The  calculation  of  the  mixture  of  the  formula  III. 
furnishes  analogous  results. 

2.  Manufacture  of  UUramarine  Blue. 

"  Blue  ultramarine  is  always  prepared  from  green 
ultramarine,  and  this  operation  presents  no  difficulty. 
The  transformation  of  the  green  product  may  be 
effected  in  different  ways ;  but  up  to  the  present  time. 


BLUE  COLORS. 


319 


manufacturers  use  one  method  only,  that  is,  a  cal- 
cination with  sulphur  at  a  low  temperature.  The 
sulphur  is  transformed  into  sulphurous  acid,  and  'a 
portion  of  the  sodium  is  oxidized,  and  is  separated 
from  the  green  ultramarine  in  the  state  of  sulphate 
of  soda.  The  sulphur  held  by  this  green  ultramarine 
remains  whole,  but  combined  with  only  a  small  quan- 
tity of  sodium. 

"  This  calcination  is  done  by  two  different  methods, 
which  may  be  called  respectively  the  French  and 
German  methods,  from  the  countries  in  which  they 
are  employed,  although  there  are  several  German 
factories  which  use  the  French  method. 

"  In  the  German  mode  of  calcination,  there  are  used 
small  cast-iron  cylinders,  imbedded  in  brickwork, 
above  a  fireplace.  The  back  part  of  each  of  these 
cylinders  is  not  movable,  and  is  provided  with  a  hole 
for  resting  in  it  one  extremity  of  the  shaft  of  a  revolv- 
ing stirrer.  The  front  part,  made  of  wrought  iron,  is 
movable,  and  has  several  holes;  one  for  the  other  end 
of  the  stirring  shaft,  a  small  one  below,  and  a  larger 
one  above,  for  the  introduction  of  the  sulphur.  All 
these  openings  may  be  closed  at  will.  There  is  another 
hole  on  top  of  the  cylinder  for  the  escape  of  the  vapors 
of  burning  sulphur,  and  an  iron  pipe  is  fitted  to  it, 
in  order  to  prevent  the  escape  of  material  during  the 
rotation  of  the  stirrer. 

"  This  cylinder  is  charged,  either  by  means  of  a 
small  shovel  passing  through  the  upper  opening,  or 
by  removing  the  front  part,  and  immediately  replacing 
it  when  the  sulphur  is  in.  At  the  same  time,  the 
shaft  of  the  stirring  apparatus  is  fixed  in  the  two 
central  holes,  and  a  crank  handle  is  attached  to  the 
projecting  part  in  front.     Each  factory  possesses 


^20 


MANUFACTURE  OF  COLORS. 


several  such  cylinders,  and  their  number  depends  upon 
the  size  of  the  works.  Up  to  the  present  time,  these 
cylinders  have  been  made  of  cast-iron,  although  clay 
seems  to  be  just  as  good,  and  even  more  durable. 

"  The  lire  being  lighted,  the  cylinder  is  charged 
with  12  to  15  kilogrammes  of  green  ultramarine  and 
closed.  The  stirrer  is  moved  now  and  then,  in  order 
to  heat  the  ultramarine  uniformly.  When  the  tem- 
perature has  been  raised  to  the  point  at  which  a  small 
quantity  of  sulphur,  projected  through  the  upper 
opening,  will  become  inflamed,  the  fire  is  moderated, 
so  as  not  to  increase  the  heat.  Half  a  kilogramme  of 
sulphur  is  then  charged  in,  the  stirrer  is  revolved, 
and  the  upper  opening  is  left  open  to  admit  the  air 
necessary  for  the  combustion  of  the  sulphur.  After- 
wards, the  stirrer  is  revolved  more  slowly,  until  it  is 
seen  that  all  the  sulphur  is  burned  out.  A  sample 
of  the  powder,  being  taken  out  with  a  small  iron 
spoon,  appears  of  a  bluish-green  color.  More  sulphur 
is  added,  stirred,  and  burned  as  long  as  the  intensity 
of  color  increases.  "When  the  maximum  of  intensity 
is  reached,  the  pigment  will  lose  its  qualities  if  this 
treatment  be  longer  continued.  The  powder  is  then 
scraped  out  into  a  sheet-iron  box,  which  also  receives 
the  small  quantities  of  material  which  fall  during  the 
operation.  A  new  charge  of  green  ultramarine  is 
immediately  put  into  the  cylinder. 

"In  many  localities,  the  last  calcination  is  done 
according  to  the  method  we  have  just  described, 
except  that  there  is  an  immediate  washing,  grinding, 
drying,  and  sifting,  before  the  ultramarine  has  become 
entirely  blue.  In  this  manner,  the  coloring  is  more 
uniform,  because  there  are  no  more  green  specks  in- 
side or  out. 


BLUE  COLORS. 


321 


"  The  blue  calcined  colors  are  ready  for  the 
market,  when  they  have  been  washed,  dried,  and 
sifted. 

"  The  intensity  of  the  blue  color  depends  on  that  of 
the  green,  but  grinding  generally  diminishes  the 
depth  of  the  color.  Light  blues  are  sometimes  pro- 
duced in  the  course  of  manufacture,  and  these  mixed 
with  dark  ones  form  the  medium  quality.  But,  most 
generally,  the  light-colored  qualities  are  produced  by 
the  addition  of  white  pigments. 

"  In  the  French  method  of  calcination,  muffles  are 
used,  that  is,  a  furnace  into  which  the  flame  of  the 
fireplace  does  not  penetrate.  Fig.  56  is  a  longitudinal 
section  of  a  furnace  of  that  kind.  Fig.  57  a  transverse 


Fig.  56.  Fig.  57.  Fig.  58. 


section,  and  Fig.  58  a  horizontal  section  at  the  level 
of  the  bed  of  the  muffle. 

"  The  fireplace  a  is  placed  under  the  bed  b,  which 
rests  upon  a  low  arch.  Several  flues,  q  q  conduct 
the  flame  into  the  space  left  between  the  dome  d  d  of 
the  muffle,  and  the  concentric  arch  e  e  of  the  furnace, 
c  is  the  chimney.  The  fireplace  a  is  composed  of 
grate  bars  a  a,  an  ash-pit  5,  and  doors  c  c.  In  front 
of  the  muffle  there  is  an  opening/,  closed  by  a  slid- 
ing-door  d,  which  may  be  raised  or  lowered  by  means 
of  a  counter-weight  and  pulley.    This  opening  is 


322 


MA^^^UFACTURE  OF  COLORS. 


covered  by  an  arched  mantle  g  g,  which  conducts  the 
sulphur  fumes  to  the  chimney,  and  prevents  them 
from  passing  into  the  work-room.  All  the  parts  in 
direct  contact  with  the  fire  are  built  of  good  fire- 
brick, cut  and  polished  by  friction  upon  each  other. 
The  number  of  muffle  furnaces  depends  on  the  size  of 
the  works. 

"  The  green  ultramarine  is  evenly  spread  upon  the 
bed,  in  layers  4  to  5  centimetres  thick.  The  door  is 
then  closed,  and  the  fire  urged  until  the  sulphur  pro- 
jected into  the  muffle  becomes  inflamed.  A  shovel- 
full  of  sulphur  is  charged  in,  and  stirred  with  an  iron 
hook,  the  door  being  raised  just  enough  to  allow  of 
the  motion  of  the  hook.  After  the  combustion  of 
this  sulphur,  and  an  examination  of  a  sample,  a  new 
quantity  of  sulphur  is  charged  in,  stirred,  and  so  on, 
until  the  consecutive  samples  show  no  improvement 
in  the  purity  and  intensity  of  the  color.  No  greater 
heat  is  required  than  that  necessary  for  the  sulphur 
to  catch  fire  as  soon  as  it  is  put  in. 

"  The  transformation  of  green  ultramarine  into  blue 
is  more  rapid  with  this  mode  of  operation,  than  with 
the  cylinders,  because  there  is  greater  access  of  the 
air,  and  therefore  more  sulphurous  acid  produced, 
and  less  volatilization  of  sulphur.  As  soon  as  the 
ultramarine  has  acquired  the  desired  color,  it  is  raked 
out  into  a  sheet-iron  box  placed  under  the  door.  The 
furnace  is  charged  again,  and  the  operation  progresses 
as  before.  We  have  already  indicated  the  further 
treatment  of  the  color. 

"  When  ultramarine  blue  is  washed  by  the  process 
of  displacement,  there  are  obtained  quite  concentrated 
solutions  of  sulphate  of  soda,  which  may  be  utilized 
after  precipitating  by  lime  the  iron  contained  therein. 


BLUE  COLORS. 


323 


"  Ultramarine  increases  in  weight  by  its  combina- 
tion with  sulphur,  and  the  increase,  after  washing 
the  product,  may  amount  to  several  hundredths.  If 
the  washings  have  not  been  thorough,  the  ultra- 
marine will  form  compact  masses  in  the  packing 
barrels." 

In  further  researches  upon  ultramarine,  Mr.  J.  G. 
Gen  tele  has  ascertained  that  ultramarine  green,  boiled 
for  a  long  time  with  a  solution  of  sal  ammoniac,  and 
then  transformed  into  blue  ultramarine,  possesses  a 
purer  color  and  a  lesser  greenish  tinge  than  any  of 
the  ultramarines  which  have  not  been  treated  in  this 
manner. 

He  concludes  from  these  experiments,  that  sal  am- 
moniac (and  probably  gaseous  and  dry  hydrochloric 
acid)  is  the  most  remarkable  bluing  agent  of  ultra- 
marine green,  because,  even  employed  in  great  excess, 
it  does  not  act  upon  the  ultramarine  blue  already 
formed. 

L.  Furstenau  Process. 

The  old  methods  of  manufacturing  ultramarine, 
such  as  have  been  introduced  into  the  majority  of  the 
South  German  works,  and  are  still  retained  in  certain 
localities,  are  so  inconvenient,  especially  when  great 
quantities  of  a  given  product  are  to  be  prepared,  that 
many  attempts  have  been  made  to  modify  them. 

Several  Rheinish  manufacturers  have  devised  the 
preparation  of  ultramarine  in  a  large  reverberatory 
furnace,  the  bed  of  which  is  first  heated  below,  and 
then  above,  by  the  returning  flame.  These  furnaces 
contain  enough  material  to  produce  about  600  kilo- 
grammes of  ultramarine,  but  their  construction  is 
such  that  the  calcination  is  not  regular  and  uniform. 


324 


MANUFACTURE  OF  COLORS. 


and  that  the  substances  are  not  protected  against 
impurities. 

This  consideration  has  determined  Mr.  C.  Fiir- 
stenau  to  propose  another  method,  which  seems  to 
obviate  all  the  inconveniences  named,  and  which 
allows  of  the  treatment  of  large  quantities  of  material 
without  the  introduction  of  dust  and  impurities.  At 
the  same  time  the  success  of  the  operation  does  not 
depend  on  the  men  so  much  as  before. 

The  ultramarine  is  calcined  in  fire-clay  boxes,  which 
may  hold  from  300  to  350  kilogrammes  of  material, 
and  which  are  located  on  each  side  of  a  double  rever- 
beratory  furnace,  resembling  a  smalt  furnace,  but 
with  a  lower  fireplace. 

This  furnace  is  composed  of  two  stories  A  and  b, 
the  lower  one  being  heated  by  the  direct  heat  of  the 
fireplace,  and  the  upper  one  by  the  hot  gases  of  the 
combustion.  The  internal  chimney,  the  arch,  and  the 
bed  of  the  first  story  are  built  of  fire-bricks  ;  ordinary 
bricks  are  employed  for  the  second  story;  the  pillars 
and  outside  work  are  of  stone.  The  bed  of  the  upper 
story  A  is  covered  with  cast-iron  plates,  in  order  to 
avoid  the  wear  and  tear  resulting  from  the  introduc- 
tion and  removal  of  the  calcining  boxes.  The  boxes 
themselves  are  made  of  fire-clay  slabs,  25  millimetres 
thick,  with  joints  rabbeted  and  luted  with  clay.  All 
of  these  joints  are  strengthened  externally,  in  order 
to  possess  the  required  firmness. 

The  composition  for  dark  alum  ultramarine  is  as 
follows : — 


Kaolin,  slightly  calcined 

Calcined  soda  ash  (95°) 

Kefi.ned  roll  sulphur 

Colophony 

Dry  pine  charcoal 


100  parts  in  weight. 


90 

u 

u 

100 

u 

6 

u 

u 

4 

u 

u 

BLUE  COLORS. 


325 


Each  of  these  substances,  with  the  exception  of 
the  colophony,  is  reduced  to  a  fine  powder  in  revolv- 
ing barrels  by  means  of  cannon  balls.  These  barrels 
or  tuns  are  of  beech  wood,  a  little  over  1  metre  in 
length,  0.65  metre  at  the  largest  diameter,  and  0.55 
in  diameter  at  the  ends.  The  staves  are  from  20  to 
30  millimetres  thick.  These  tuns  are  closed  like 
those  used  for  amalgamating,  and  the  aperture  is  13 
to  14  centimetres  in  diameter,  with  a  felt  packing  for 
preventing  the  escape  of  the  powder. 

The  cannon  balls  employed  are  from  7  to  8  centi- 
metres in  diameter,  and  about  18  kilogrammes  of 
them  are  introduced  into  each  tun.  The  velocity  is 
equal  to  36  revolutions  per  minute. 

As  soon  as  the  materials  have  become  sufficiently 
comminuted  they  are  mixed  with  colophony,  broken 
into  pieces  of  the  size  of  walnuts,  and  the  mixture  is 
made  to  rotate  for  four  hours  more.  The  resulting 
grayish  powder  is  placed,  without  packing  it  tight, 
in  the  fire-clay  boxes.  These  are  closed,  and  then 
introduced  into  the  furnace.  When  all  the  apertures 
of  the  furnace  have  been  luted,  the  fire  is  urged  to 
bring  the  temperature  as  rapidly  as  possible  to  the 
melting  point  of  an  alloy  composed  of  equal  parts  of 
gold  and  silver.  This  temperature  is  kept  up  for 
five  to  six  hours,  and  the  fire  is  watched  by  an  opening 
left  in  the  cleaning  flue.  In  order  to  ascertain  the 
state  of  the  composition,  there  is  a  small  clay  pipe,  25 
millimetres  in  diameter  in  the  clear,  one  end  of  which 
penetrates  the  calcining  box,  while  the  other  end  pro- 
jects about  5  centimetres  from  the  furnace  wall.  Sam- 
ples are  taken  now  and  then  with  a  small  iron  spoon 
passed  through  this  pipe,  and  resembling,  on  a  smaller 
scale,  the  tools  used  for  removing  the  powder  from 


326 


MAOTFACTURE  OF  COLORS. 


blast  holes.  If,  after  cooling,  these  samples  become 
green,  the  fire  is  allowed  gradually  to  die  out,  the 
chimney-damper  is  closed,  and  the  furnace  is  per- 
mitted to  cool  otf  for  twenty-eight  hours. 

After  two  days  the  bluish-green  mass  is  extracted 
from  the  boxes,  ground  under  vertical  stones,  and 
still  more  finely  comminuted  in  revolving  tuns. 
The  powder  is  then  charged  in  cast-iron  boxes,  45 
centimetres  high,  having  a  length  of  65  centimetres 
on  top  and  55  on  the  bottom,  and  a  width  of  55  centi- 
metres on  top  and  50  on  the  bottom.  The  thickness 
of  the  metal  is  5  millimetres.  These  boxes  are  well 
closed  with  iron  covers,  and  then  introduced  before 
the  fire  is  begun,  into  the  upper  part  of  the  furnace, 
which  may  contain  nine  of  them ;  they  remain  there 
until  twelve  hours  after  the  fire  is  run  down.  This 
mode  of  oxidation  and  of  desulphurization  is  imitated 
from  the  mode  of  oxidizing  red  lead,  and  may  be 
repeated  without  impairing  the  color. 

The  blue  thus  obtained  is  carefully  washed  and 
finely  ground  in  water  under  horizontal  quartz  or 
granite  stones.  The  revolving  stone  is  in  perfect 
equilibrium,  and  the  surfaces  of  the  two  stones  should 
be  polished  by  grinding  a  mixture  of  sand  and  clay 
in  water.  The  lower  stone  is  tightly  inclosed  within 
a  kind  of  ring,  which  rises  10  centimetres  above  the 
top  of  the  upper  stone,  and  which  is  closed  with  a 
cover.  The  circumference  of  the  upper  stone  is  pro- 
vided with  two  inclined  bands  of  sheet  iron,  which 
scoop  the  pigment  and  bring  it  on  top,  in  order  to  pass 
again  between  the  two  grinding  surfaces.  With  a 
revolving  stone  1  metre  in  diameter,  the  velocity  is 
fifteen  revolutions  per  minute.  A  charge  is  com- 
posed of  25  kilogrammes  of  powder  plus  the  quantity 


BLUE  COLORS. 


327 


of  water  necessary.  As  soon  as  the  color  has  acquired 
the  desired  brightness  and  firmness,  which  point  is 
ascertained  by  examining  a  dried  sample,  the  paste  is 
received  and  drained  in  cloth  bags,  and  then  dried  in 
cast-iron  pots,  placed  in  the  upper  portion  of  the 
furnace  after  the  calcining  boxes  have  been  removed. 
The  dry  color  is  sifted  and  packed  for  the  market. 


^Notwithstanding  the  researches  of  Gmelin,  Tire- 
mon,  Weger,  Pruckner,  Winterfeld,  Brunner,  Dippel, 
Buchner,  Habich,  and  Gentele,  we  see  that  there  still 
exists  a  great  deal  of  incertitude  relative  to  the  com- 
position and  mode  of  formation  of  artificial  ultrama- 
rine. More  recently,  Mr.  H.  Ritter,  of  Lilnebourg, 
has  tried  to  throw  some  light  on  this  subject,  and  he 
has  made  known  the  results  of  his  experiments  in  a 
work  published  at  Goettingen,  in  1860,  under  the 
title  of  TJhei'  das  UUramarin,  which  should  be  con- 
sulted by  all  persons  interested  in  this  manufacture. 

The  most  interesting  part  of  the  work  of  Mr. 
Eitter  is  the  discovery  of  a  white  ultramarine  pro- 
duced at  a  temperature  of  900  to  950°  C,  which  de- 
monstrates that  the  sulphide  of  iron  is  not  the  coloring 
principle  of  ultramarine,  either  green  or  blue. 

This  white  ultramarine,  which  is  easily  transformed 
into  green  and  blue  ultramarine,  is  composed  of — 

Silica   39.66 

Alumina   31.11 

Soda   14. t5 

Potassa   1.60 


M.  White  Utramarine. 


Sulphide  of  sodium 
Bisulphide  of  sodium 
Sulphide  of  iron 


8.09 
4.88 
0.11 


100.26 


328 


MA^^LTFACTURE  OF  COLORS. 


The  experiments  of  Mr.  Ritter  have  been  published 
through  extracts  in  the  Technologiste,  yo\.  xxii.,  'No.  for 
March,  1861.  They  are  too  extensive  to  reproduce 
here,  and  we  shall,  therefore,  give  only  the  conclusions 
of  the  work. 

1.  The  combination,  which  takes  place  during  the 
calcination  of  the  sulphide  of  sodium  and  the  silicate 
of  alumina,  is  colorless;  it  is  formed  of  silicate  of 
soda,  silicate  of  alumina,  and  a  monosulphide,  with  a 
small  proportion  of  poly  sulphide  of  sodium ;  but  it 
contains  no  oxidized  combinations  of  sulphur. 

2.  If  a  portion  of  the  sodium  be  removed  (by  chlo- 
rine or  sulphurous  acid,  for  instance)  from  the  sul- 
phide of  sodium  of  white  ultramarine,  the  proportion 
of  sulphur  corresponding  to  this  eliminated  sodium 
combines  with  the  remaining  sulphide  of  sodium  and 
forms  a  polysulphide. 

3.  The  white  ultramarine  thus  transformed  becomes 
ultramarine  blue  by  the  absorption  of  oxygen,  that 
is,  by  an  oxidized  combination  of  sulphur  with  a 
portion  of  the  sulphide  of  sodium.  This  blue  ultra- 
marine is  a  combination  of  silicate  of  soda,  silicate  of 
alumina,  a  polysulphide  of  sodium,  and  a  soda  salt 
with  an  acid  from  the  sulphur. 

4.  The  sulphide  of  potassium,  calcined  with  silicate 
of  alumina,  does  not  form  a  combination  similar  to 
that  of  ultramarine,  but  there  results  only  a  silicate 
of  alumina  and  potassa  without  sulphur. 

5.  Moreover,  it  is  very  probable  that  the  oxidized 
combination  of  sulphur,  held  in  blue  ultramarine,  is 
a  hyposulphite  or  a  sulphite  of  soda,  and  the  former 
hypothesis  seems  the  more  likely. 


BLUE  COLORS. 


329 


N.    Trial  and  Analysis  of  Ultramarines. 

L  Mr.  Guimet  has  proposed  the  following  manner 
of  comparing  ultramarines  : — 

"  I  weigh,"  says  he,  "  a  decigramme  of  each  sample 
of  ultramarine  to  be  tried,  and  as  many  times  6  deci- 
grammes of  white  as  there  are  samples  of  ultramarine. 
The  white  I  use  is  the  best  quality  of  Meudon  white 
(chalk),  which  I  keep  in  a  bottle  large  enough  to 
hold  material  for  1000  trials. 

"  I  then  mix  upon  a  white  marble  slab,  or,  more 
simply,  upon  a  piece  of  smooth  and  well-sized  paper, 
1  decigramme  of  blue  and  6  decigrammes  of  white. 
This  operation  is  effected  rapidly  by  using  a  flexible 
painter's  knife,  with  which  the  blue  and  white  are 
crushed  and  mixed,  until  the  whole  presents  to  the 
eye  no  difference  of  coloration. 

'^Let  us  now  suppose  that  we  have  made  four 
mixtures,  having  each  a  different  degree  of  colora- 
tion; it  is  evident  that  the  ultramarine  which  has 
produced  the  greatest  intensity  of  coloration  is  the 
richest  and  the  most  valuable. 

Taking  now  the  darkest  and  the  lightest  samples, 
I  try,  by  successive  additions  of  white,  to  render  the 
tone  of  the  dark  one  equal  to  that  of  the  light  one ; 
and  if  I  have  had  to  use  6  decigrammes  more  of  white, 
I  conclude  that  the  blue,  which  bears  twice  as  much 
white  to  produce  the  same  azure  tone,  is  twice  as  rich 
in  coloring  power,  and  twice  as  valuable  in  money 
value. 

"  I  have  chosen  a  simple  ratio  to  render  my  reason- 
ing more  clear;  but  we  understand  that  this  trial  will 
give  us  very  approximately  the  relative  values  of  blues. 

"  Sensible  scales  are  necessary  for  weighing  1  deci- 


330 


MANUFACTUliE  OF  COLORS. 


gramme;  but  with  ordinary  scales,  the  weight  of  the 
samples  may  be  increased.  For  instance,  we  may 
take  1  gramme  of  blue  and  6  grammes  of  white ;  the 
only  inconvenience  is  that  the  mixing  is  a  little  longer. 

"It  results  from  the  above  stated  facts,  that  ultra- 
marine blues  have  a  value  in  a  direct  ratio  to  their 
coloring  power.  This  property  is  generally  due  to 
the  fineness  of  the  pigment.  A  great  degree  of  com- 
minution is  always  advantageous,  but  it  is  absolutely 
necessary  for  artistic  painting  and  calico  printing. 
On  that  account,  I  prepare  special  qualities  for  these 
uses,  although  I  pay  a  great  deal  of  attention  to  the 
grinding  of  all  my  blues. 

u  The  results  agree  with  what  I  have  said,  since  the 
paper  manufacturers  prefer  my  blue  to  all  others, 
even  at  a  higher  price.  Most  of  my  production  is 
thus  sold,  especially  in  foreign  countries. 

Calico  printers  want  bright  and  very  finely  ground 
blues;  my  dark  quality  is  generally  preferred,  since 
it  is  better  fixed  upon  the  cloth,  and  does  not  scratch 
the  printing  rollers." 

II.  Ultramarine,  says  Mr.  J.  P.  Dippel,  is  distin- 
guished from  all  the  other  blue  pigments  by  its  ex- 
ternal appearance,  especially  by  its  soft  qualities,  and 
the  intensity  and  purity  of  its  color. 

A  simple  i^rocess  for  distinguishing  ultramarine 
from  other  pigments  which  resemble  it,  Thenard  or 
cobalt  blue  for  instance,  consists  in  moistening  the 
sample  with  hydrochloric  acid.  Ultramarine  is  en- 
tirely decolorized,  and  there  is  produced  sulphuretted 
hydrogen,  which  is  easily  recognized  by  its  smell. 

An  addition  of  indigo  is  detected  by  heating,  and 
this  substance  emits  purple  vapors.  Mountain  blue 
becomes  greenish,  and  lastly  black,  by  heat.  Prussian 


BLUE  COLORS. 


331 


blue  becomes  brown  when  heated,  or  boiled  with  a 
solution  of  caustic  potassa.  Smalt  and  cobalt  blue 
preserve  their  color  in  acids. 

A  good  ultramarine  should  be  of  a  dark-blue  color, 
without  grit  and  foreign  admixtures.  Ground  with 
oil,  it  should  not  be  decolorized  by  being  heated  in  a 
crucible,  or  upon  a  red-hot  piece  of  iron.  It  should 
also  dissolve  in  concentrated  acids  without  efferves- 
cence. 

In  order  to  determine  the  value  of  ultramarines, 
pieces  of  paper  are  colored  with  the  different  samples, 
and  the  tones  of  color  are  compared.  While  the  ultra- 
marine is  mixed  with  a  solution  of  glue  or  gum,  if  we 
observe  a  red  or  brown  substance  of  a  dirty  color  on 
the  surface  of  the  liquor,  this  ultramarine  contains  an 
excess  of  sulphide  of  sodium,  which  will  change  its 
color  when  used. 

As  it  is  possible  that  pipe-clay  has  been  added  to 
the  ultramarine  during  the  bluing  calcination,  in  order 
to  obtain  light  tones  of  color,  the  darkest  kinds  should 
generally  be  preferred.  However,  we  should  remark 
that  there  are  ultramarines  which,  by  an  energetic 
calcination,  have  acquired  more  durability,  but  which 
are  lighter  colored.  These  are  in  no  way  inferior  to 
the  dark  kinds. 

III.  Mr.  C.  P.  Priickner,  chemist  and  manufacturer 
at  Hof,  has  found  a  process  for  determining  the  quality 
and  durability  of  ultramarines,  by  a  treatment  with 
hydrogen.  This  gas,  at  a  certain  temperature,  re- 
moves the  sulphur  from  the  ultramarine,  and  renders 
it  reddish.  Therefore,  by  heating  the  ultramarine  in 
a  glass  tube,  connected  with  a  hydrogen  generator, 
and  passing  the  gas  through,  this  chemist  has  obtained 


332 


MANUFACTURE  OF  COLORS. 


the  following  results  with  several  samples  of  ultra- 
9  marine  at  his  disposal: — 

1.  Artificial  ultramarine  of  the  first  quality  (No. 
0). — This  ultramarine  began  to  turn  reddish,  and 
after  half  an  hour  the  blue  color  had  entirely  disap- 
peared and  passed  to  a  greenish-gray. 

2.  Inferior  qualities, — The  inferior  qualities  of  arti- 
ficial ultramarine  lose  their  color  more  rapidly.  The 
No.  5  of  Nuremberg  manufacture  was  decolorized 
after  a  few  mimdes^  and  became  a  grayish-white. 

3.  A  sample  bought  at  Venice  by  Mr.  Priickner, 
and  certified  to  have  been  prepared  from  broken  pieces 
of  lapis  lazuli,  was  submitted  to  the  same  treatment. 
After  one  hour^  its  color  was  still  sensibly  blue. 

4.  x\  sample  of  a  remarkably  fine  native  ultrama- 
rine, left  in  1805  (at  w^hich  time  no  artificial  ultrama- 
rine was  manufactured)  in  the  corner  of  a  pharmacy 
as  a  useless  substance,  was  treated  in  the  same  man- 
ner. After  two  hours  of  contact  with  hydrogen  gas 
in  a  hot  tube,  all  the  color  was  not  destroyed. 

"  It  results  from  these  observations,"  Mr.  Priickner 
adds,  "  that  artificial  ultramarine  treated  by  hydrogen 
behaves  difierently  from  real  native  ultramarine  pre- 
pared from  lazulite,  and  it  is  probable  that  a  similar 
result  will  be  observed  in  painting.  A  similar  exam- 
ple is  found  in  cinnabar ;  the  product  prepared  by  the 
wet  way  presenting  properties  entirely  different  from 
the  cinnabar  produced  by  the  dry  way,  or  sublimed, 
when  it  is  employed  in  the  manufacture  of  wafers 
and  sealing  wax.  The  former  especially,  when  colored 
by  cinnabar  (vermilion)  prepared  by  the  wet  process, 
are  more  blackish-red  than  intensely  red.  The  same 
effect  is  seen  with  sealing  wax,  although  the  vermilion 


BLUE  COLORS. 


333 


(Avet  way)  is  brighter  than  that  which  has  been 
sublimed. 

"  Generally  speaking,  the  durability  of  color  of  ul- 
tramarine is  influenced  by  the  fixity  of  the  substances 
entering  into  its  composition,  and  by  the  intensity  of 
the  calcination.  Repeated  heatings  in  closed  vessels 
increase  the  durability  of  ultramarine,  but  they  are 
always  accompanied  by  a  diminution  in  the  intensity 
of  the  color,  which  may  become  a  pale  blue.  By  this 
process,  the  ultramarine  acquires  such  a  durability 
that  acids  do  not  destroy  this  pale  blue  color." 

lY.  Mr.  W.  Biichner  has  made  a  special  study  of 
the  practical  testing  of  artificial  ultramarines.  The 
following  is  his  mode  of  operation  : — 

(a.)  Resistance  to  the  action  of  atum, — As  there  is 
no  ultramarine  which  will  completely  resist  for  a  long 
time  a  hot  and  saturated  solution  of  alum,  we  must, 
for  those  kinds  of  tests,  remain  within  the  limits  of 
technical  operations,  and  draw  conclusions  only  after 
check-tests  have  been  made  with  different  ultrama- 
rines. The  length  of  time  required  for  the  action  of 
an  alum  solution  upon  ultramarine  is  an  important 
consideration,  and  requires  comparative  trials.  We 
should  here  remark,  that  a  coarse-grained  ultrama- 
rine resists  the  action  of  alum  better  than  an  ordinary 
ultramarine  ;  it  is  not,  however,  suitable  for  paper 
manufacturers  and  calico  printers,  on  account  of  its 
feeble  coloring  power,  and  the  coarseness  of  its  grain. 

Such  experiments  require,  1st,  a  saturated  and  cold 
solution  of  alum;  2d,  a  few  test  glasses;  3d,  a  deli- 
cate scale  ;  4th,  a  graduated  burette. 

Five  centigrammes  of  the  ultramarine  to  be  tested 
are  weighed  carefull}^,  and  placed  in  a  glass,  which  is 
marked  with  a  suitable  sign  or  number,  when  com- 


334  MAWFACTURE  OF  COLORS. 


parative  experiments  are  going  on  at  the  same  time. 
Then  an  accurately  measured  volume  of  the  cold  and 
saturated  alum  solution  is  poured  upon  the  color,  and 
the  whole  is  stirred  with  a  glass  rod.  After  a  few 
minutes,  several  hours,  or  several  days,  we  may  see 
how  the  destruction  of  the  ultramarine  color  pro- 
gresses, and  its  degree  of  resistance.  An  ultramarine 
which  with  an  equal  coloring  power  resists  the  longer, 
is  evidently  the  better.  The  reaction  may  be  rendered 
more  rapid  by  immersing  all  the  test  glasses  in  the 
same  vessel  holding  hot  water.  If  we  consider  that 
in  the  manufacture  of  paper,  the  pulp  becomes  sen- 
sibly heated  during  the  work,  this  last  experiment 
shows  why  we  should  prefer  an  ultramarine  which 
resists  the  action  of  alum.  But  in  order  to  arrive  at 
a  still  more  technical  conclusion,  we  may,  instead  of 
a  pure  alum  solution,  employ  a  solution  of  glue  in 
which  alum  is  added.  By  cooling,  the  ultramarine 
remains  suspended  in  the  jelley,  and  the  action  is 
more  energetic. 

(h.)  Trial  of  the  coloring  power, — The  aspect  of  a 
color,  whether  dark  or  clear,  is  the  result  of  the  refrac- 
tion of  light,  and  it  is  well  known  that  colors  appear- 
ing alike  may  possess  a  coloring  power  widely  diflPer- 
ent.  In  order  easily  to  ascertain  the  difference,  it  is 
necessary  to  dilute  the  color  with  a  powdered  white 
body.  The  apparatus,  etc.,  consist  of  a  delicate  pair 
of  scales,  a  mixing  dish,  and  a  certain  quantity  of 
lenzinite,^  sulphate  of  baryta,  or  white  lead.  One 
gramme  of  lenzinite  and  five  centigrammes  of  ultra- 
marine are  carefully  mixed  in  the  dish,  but  without 

*  Lenzinite  is  a,  kind  of  white  cla\^,  found  in  scattered  lumps 
near  Kali,  in  the  Eifeld. 


BLUE  COLORS. 


335 


grinding.  The  other  samples  are  worked  in  the  same 
manner,  and  when  the  comparison  is  made,  it  is  often 
a  subject  of  astonishment  to  see  the  difference  in 
coloring  power  of  certain  kinds  of  ultramarine.  It 
is,  of  course,  necessary  that  these  experiments  should 
be  made  with  scrupulous  exactness,  and  an  un- 
practised eye  may  cause  great  mistakes.  The  mix- 
tures are  placed  one  near  the  other,  or  one  upon  the 
other,  and  they  are  slightly  compressed  with  the 
spatula.  Or  they  may  be  put  into  glasses  with  equal 
volumes  of  water.  The  distinction  should  be  made 
only  when  the  difference  in  tint  or  hue  is  perfectly 
apparent.  The  hue  may  sometimes  be  a  pale  blue,  or 
a  greenish-blue,  or  a  reddish-blue,  or  a  pink  blue. 
But  the  most  intense  color  will  always  be  recognized. 

It  now  remains  to  be  seen  which  of  these  kinds 
are  the  best.  It  seems  proven  that  the  pure  blue  red 
qualities  are  the  best  for  paper  manufacturers,  calico 
printers,  and  paint  grinders,  and  that  the  greenish- 
blue  ones  are  more  advantageous  for  fancy  papers. 

For  a  long  time,  I  had  the  idea  to  express  the 
coloring  power  as  is  done  in  estimating  the  power  of 
alcohol,  bleaching  powder,  etc.,  by  a  scale,  but  we 
have  no  unit  upon  which  to  base  ourselves,  and,  if  for 
ultramarine  a  scale  were  to  be  constructed  from  the 
best  sample,  this  same  sample  should  be  in  the  hands 
of  all  those  who  make  similar  tests.  In  order  to  ren- 
der the  operation  possible,  I  have  under  the  name  of 
ultramarinometer  {ultramarinomesser\  adopted  a  nor- 
mal or  standard  color,  the  mixture  of  which  with  any 
kind  of  white  substances,  gives  the  degree  of  the  scale. 

Any  person  having  a  few  grammes  of  this  color,  or 
an  ultramarine  of  the  same  coloring  power,  may 


336  MAi^^urACTURE  or  colors. 

determine  the  coloring  power  of  any  sample,  with  the 
following  table : — 

Scale  of  the  Ultramarinometer. 

2  grammes  of  lenzinite  with  0.5  gramme  of  ultramarine  g  ve  10°  of  coloring  power. 


0.3  "  "  9 

"              ««  0.2  "  "  8 

(I              .*  0  1  "  7 

««              '«  0.05  "  "  6 

««              "  0.03  "  "  5 

<«              it  0.02  •«  "  4 

a               ((  0  01  "         .  "  3 

'«              '«  0.005  "  2 

"  0.003  «'  "  1 


When  the  above  scale  has  been  prepared,  2  grammes 
of  lenzinite  are  mixed  with  0.5  gramme  of  ultramarine, 
and  the  mixture  is  compared  with  those  of  the  scale. 
That  with  which  the  tested  mixture  agrees  the  best 
gives  the  degree  of  the  coloring  power  of  the  sample 
of  ultramarine. 

(c.)  Trial  of  the  printing  poiuer, — A  substance 
suitable  for  printing  should  be  finely  comminuted 
and  require  little  thickening.  The  degree  of  fineness 
may  be  ascertained  with  a  magnifying  glass,  or  by 
rubbing  the  powder  with  the  finger  upon  a  piece  of 
writing  paper.  If  the  substance  contains  coarse  por- 
tions, and  is  not  fine  and  homogeneous,  it  will  be 
perceived  by  the  sense  of  feeling.  If  no  coarse  grains 
are  felt,  and  if,  after  striking  the  paper  from  under- 
neath, a  notable  portion  of  the  ultramarine  remains 
adhering  to  the  paper,  this  ultramarine  appears  to 
answer  the  purpose.  A  pinch  of  this  powder  is  also 
rubbed  against  a  polished  piece  of  brass,  which  should 
not  be  scratched  by  it.  But  the  best  proof  is  that  of 
the  coloring  power,  because  when  it  is  high  the  de- 
gree of  comminution  must,  of  course,  be  satisfactory, 


BLUE  COLORS. 


337 


taking  however  into  consideration  the  accidental  im- 
purities which  are  often  to  be  found. 

(d.)  Trial  of  the  glazing  jpoioer. — The  property  in 
ultramarine  of  acquiring  a  glaze  is  an  advantage 
sought  for  in  many  of  its  applications.  This  property 
supposes  a  great  fineness  of  body,  a  high  coloring 
power,  and  the  necessity  of  but  a  small  amount  of 
size.  A  single  coat  of  glue  size  upon  paper  will  en- 
able us  to  ascertain  this  property.  If,  after  this  size 
has  become  dry,  a  glaze  be  obtained  by  a  few  strokes 
of  a  soft  brush,  then  the  ultramarine  is  satisfactory, 
because,  in  the  manufacture  of  glazed  papers,  there 
is  always  added  a  small  quantity  of  wax  soap  in 
order  to  aid  the  fixing  of  the  printing  colors.  Such 
a  result  will  be  more  readily  obtained  by  using  a  wax 
soap,  or  brushes  charged  with  powdered  talc;  but 
even  with  these  means  no  ultramarine  will  glaze  well 
if  it  does  not  do  so  without  them. 

(e.)  Trial  for  the  proportion  of  gelatine  {size), — How- 
ever simple  such  a  problem  appears,  it  cannot  be 
solved  except  by  a  practical  trial.  A  lean  and  com- 
mon ultramarine  will  always  require  a  great  deal  of 
glue,  and,  even  with  a  good  glue,  its  adherence  will 
soon  be  defective.  A  small  quantitative  test  may  be 
made  as  follows :  A  certain  quantity  of  ultramarine 
and  glue  is  weighed,  and  the  latter,  after  solution  in 
water,  is  put  into  a  graduated  vessel.  Then  by  adding 
this  solution  to  the  blue  by  small  quantities  at  a  time, 
and  reading  the  number  of  divisions  left  after  the 
proper  result  is  obtained,  we  know  the  proportion  em- 
ployed. The  sizing  should  be  such  that  no  ultrama- 
rine will  be  removed  when  the  paper  thus  colored  is 
dry  and  is  rubbed  with  another  piece  of  white  paper. 

It  is  well  known  that  moderate  prices  increase  the 
22 


338 


MANUFACTURE  OF  COLORS. 


consumption  of  a  product  considerably,  and  the  em- 
ployment of  ultramarine  will  attain  enormous  pro- 
portions when  it  shall  be  possible  to  obtain  it  at  a 
low  price.  On  the  other  hand,  when  the  selling  price 
is  scarcely  above  the  cost,  the  manufacturer  is  weighed 
down  and  cannot  undertake  improvements.  The  ap- 
plications are  therefore  limited  on  account  of  the  im- 
perfection or  of  the  inferior  quality  of  the  product. 
In  regard  to  ultramarine,  the  comparison  of  the  prices 
of  difierent  manufacturers  will  never  be  satisfactory 
if  the  color  of  the  product  be  alone  considered  ;  be- 
cause it  is  a  well-known  fact  that  two  kinds  of  ultra- 
marine, similar  in  appearance,  may  be  different  in 
their  coloring  power,  and  vary  in  price  as  100  does  to 
200,  independently  of  the  other  properties.  Therefore, 
if  we  desire  to  establish  comparisons  of  prices,  it  is 
absolutely  necessary  that  we  should  take  into  ac- 
count the  intimate  properties  of  ultramarine  in  order 
to  arrive  at  its  real  value. 

Y.  Mr.  Barreswill  has  indicated  the  following  pro- 
cess for  ascertaining,  very  approximately,  the  value 
of  ultramarine : — 

An  artificial  sulphate  of  baryta  is  prepared  by  de- 
composing a  solution  of  nitrate  of  baryta,  or  of 
chloride  of  barium,  with  sulphuric  acid.  The  pre- 
cipitate is  well  washed  and  dried.  Two  small 
mortars  receive  each  20  grammes  of  sulphate  of 
baryta ;  on  the  other  hand  from  0.5  to  1  gramme  of 
ultramarine  is  weighed  in  two  porcelain  dishes  of  a 
known  weight.  One  of  these  dishes  contains  the 
standard  ultramarine,  and  the  other  the  sample  to  be 
compared.  A  certain  proportion  of  the  standard  blue 
is  then  mixed  with  the  sulphate  of  baryta,  and  small 
portions  of  the  tested  sample  are  added  to  the  baryta 


BLUE  COLORS. 


339 


of  the  other  mortar,  until  the  two  tints  have  the  same 
intensity.  Weighing  now  the  ultramarines  left  in 
both  dishes,  the  differences  of  weight  give  the  com- 
parative value  desired. 

Ultramarine  is  sometimes  adulterated  with  starch, 
which  is  easily  detected  by  a  tincture  of  iodine.  The 
blue  ashes  are  recognized  by  throwing  a  pinch  of 
the  suspected  sample  into  aqua  ammonia ;  pure  ultra- 
marine produces  no  change,  whereas  the  blue  ashes 
are  dissolved  and  color  the  liquor  an  intense  blue. 

0.  Composition  of  ultramarines. 

The  blue  and  green  ultramarines  have  been  analyzed 
by  several  chemists,  who,  from  all  the  results  of 
their  analyses,  have  put  forth  theoretical  views 
which  have  not  yet  resolved  the  problem  of  their 
composition. 

Those  persons  who  may  be  interested  in  these 
questions  will  find  in  the  Repertoire  de  Cliimie  pure  et 
appliquee^  November,  1861,  p.  420,  an  excellent  re- 
sume, made  by  Mr.  A.  Scheurer-Kestner,  of  the 
opinions  of  Messrs.  Eisner,  Brunner,  Steel tzel,  Breun- 
lin,  Gentele,  Wilkens,  E-itter,  Boeckmann,  etc.  These 
opinions  often  disagree,  and  appear  to  have  been  re- 
cently overthrown  by  an  experiment  of  Mr.  E.  Guignet, 
who  has  extracted,  by  means  of  bisulphide  of  carbon, 
notable  proportions  of  sulphur  from  various  samples 
of  ultramarine,  without  decomposing  the  blue  or 
changing  its  intensity.  Artificial  ultramarines,  there- 
fore, contain  free  sulphur,  and  the  difierences  in 
coloration,  durability,  etc.,  of  these  blues  may  pos- 
sibly be  explained  by  the  greater  or  less  proportion 
of  that  sulphur.  The  greenish  tinge  of  certain  blues, 
printed  with  albumen,  and  then  submitted  to  the 


340 


MANUFACTURE  OF  COLORS. 


action  of  steam,  may  possibly  be  caused  by  the  pre- 
sence of  more  or  less  free  sulphur. 

At  all  events  the  observation  of  Mr.  Guignet  is  of 
great  practical  importance,  and  will  possibly  permit 
of  the  manufacturers  changing  their  formulae,  or  their 
mode  of  operation,  in  order  to  prepare  durable  pro- 
ducts of  a  fixed  composition. 

3d.  Cobalt  ultramarine. 
Cobalt  ultramarine,  or  Gahn's  ultramarine,  from 
the  name  of  the  inventor,  is  a  combination  of  alumina 
with  the  oxide  of  cobalt.  This  combination  does  not 
appear  to  be  in  definite  proportions,  since  it  varies 
with  the  different  works  in  which  this  pigment  is 
made. 

Its  preparation  consists  in  making  a  solution  of 
alum,  that  is,  a  double  sulphate  of  alumina  and  j)otassa 
(or  ammonia),  and  dissolving  in  it  a  certain  propor- 
tion of  nitrate,  sulphate,  or  chloride  of  cobalt.  The 
whole  is  then  precipitated  by  another  solution  of  car- 
bonate of  soda  or  potassa.  The  resulting  abundant 
and  pink-white  precipitate  is  a  mixture  of  carbonate 
of  cobalt  and  of  hydrated  alumina,  which  is  carefully 
washed  with  hot  water,  dried,  and  calcined  in  a  cru- 
cible at  a  high  temperature.  After  cooling,  the  pro- 
duct is  ground  into  a  fine  powder  which  resembles 
the  blue  ultramarine  of  the  first  quality,  but  appears 
violet  under  artificial  light.  By  varying  the  propor- 
tions of  cobalt  more  or  less  intense  tones  of  blue  will 
be  obtained.  If  a  great  purity  of  color  be  desired 
the  materials  employed  should  not  contain  iron. 

Cobalt  ultramarine  unites  quite  well  with  other 
pigments  used  in  oil  painting,  and  is  scarcely  poison- 
ous. 


BLUE  COLORS. 


341 


§  12.  Blue  ashes.    Lime  Hue,    Copper  hlue. 
Mountain  hlue. 

The  composition  of  this  color,  which  is  of  a  sky 
blue,  has  been  a  secret  for  a  long  time.  It  was  im- 
ported from  London,  and  was  prepared  with  the 
copper  resulting  from  the  treatment  of  silver  bullion. 
Pelletier  was  the  first  chemist  who,  after  having 
analyzed  a  sample  of  fine  English  blue  ashes,  suc- 
ceeded in  preparing  them  in  France.  In  order  to 
obtain  blue  ashes  of  a  constantly  fine  quality,  it  is 
necessary,  according  to  this  chemist :  1.  To  mix 
powdered  lime  with  a  weak  solution  of  nitrate  of 
copper  (CuO.NO'^),  and  to  employ  these  substances 
in  such  proportions  that  all  of  the  lime  is  saturated 
by  the  nitric  acid,  that  is,  by  keeping  always  a  certain 
excess  of  undecomposed  nitrate  of  copper  ;  2.  To 
wash  the  precipitate  several  times ;  3.  To  drain  it 
upon  a  cloth ;  4.  To  grind  it  with  7  to  10  per  cent  of 
its  weight  of  lime;  5.  To  dry  it. 

This  process,  described  by  Pelletier,  is  not  that 
followed  by  manufacturers.  It  appears  that  the 
latter  obtain  the  blue  ashes  by  pouring  a  solution  of 
commercial  potash  into  one  of  sulphate  of  copper, 
washing  the  precipitated  carbonate  of  copper,  and 
grinding  it  with  lime,  to  which  a  small  proportion 
of  sal  ammoniac  has  been  added.  This  salt,  being 
decomposed  by  the  lime,  increases  the  brightness  of 
the  color,  with  which  it  forms  a  kind  of  ammonium 
compound  of  a  deep  blue. 

Another  blue  ash,  called  arseniate  of  copper,  is 
obtained  by  dissolving  5  kilogrammes  of  arseniate  of 
potassa  in  32  litres  of  hot  water,  and  pouring  into  it 
another  solution  of  3.5  kilogrammes  of  sulphate  of 


342 


MANUFACTURE  OF  COLORS. 


copper.  The  precipitate  is  washed  with  water,  then 
drained  upon  a  cloth,  and  dried  in  the  shade. 

Blue  ashes  with  size  are  often  employed  for  the- 
atrical decorations  and  painted  papers.  They  present 
the  inconvenience  of  turning  green  after  a  few  days, 
especially  when  they  are  exposed  to  the  action  of 
solar  light.  Ground  in  oil,  they  become  dark,  and 
lose  part  of  their  beauty.  Those  made  in  England, 
of  which  we  shall  explain  the  prejDaration,  are  more 
durable.  "When  blue  ashes  are  ground  upon  a  slab 
with  a  muller,  they  feel  very  greasy,  but  afterwards 
they  become  much  more  fluid. 

I.  Manufacture  of  the  ashes  in  England, — We  have 
already  seen  that  the  nitrate  of  copper,  resulting  from 
the  parting  of  silver,  is  generally  used ;  but  it  appears 
that  any  soluble  copper  salt,  the  acid  of  which  will 
make  a  soluble  salt  with  lime,  is  just  as  convenient. 
Therefore,  the  cheap  sulphate  of  copper  may  be  first 
decomposed  by  the  acetate  of  lead  or  the  acetate  of 
lime,  and,  in  some  localities,  by  the  chloride  of  calcium. 

"We  should  observe  that,  if  we  cannot,  by  this  double 
decomposition,  accomplish  the  combining  of  exactly 
the  whole  of  the  sulphuric  acid  with  the  lime  (which, 
however,  is  not  difficult  after  a  few  trials),  it  is  pre- 
ferable to  have  a  small  excess  of  sulphate  of  copper 
in  the  liquor  rather  than  one  of  lime  salt. 

The  solution  of  copper  resulting  from  this  double 
decomposition  should  contain  but  a  very  small  pro- 
portion of  sulphate  of  lime.  It  is  filtered,  after 
having  settled  in  a  cool  place  for  at  least  24  hours. 

The  filtered  solution  is  diluted  with  pure  water 
until  its  specific  gravity  becomes  about  18°  Be. 

On  one  hand,  a  milk  of  lime  is  prepared  with  very 
white  and  well-burned  lime,  which  is  slaked  and 
mixed  with  a  large  quantity  of  pure  water.  The 


BLUE  COLORS. 


343 


milk  is  kept  stirred  for  a  long  time  in  a  lead-lined 
tnn,  having  a  stopcock  at  a  few  centimetres  above 
the  bottom.  After  one  minute  given  for  the  settling 
of  the  sand  and  other  impurities,  the  milk  of  lime  is 
drawn  out  through  the  stopcock,  and  is  then  allowed 
to  settle  entirely  in  other  vessels  lined  with  lead,  or 
in  copper  pans.  When  the  deposit  has  acquired  a 
certain  consistency,  it  is  ground  in  a  mill  similar  to 
those  employed  for  indigo,  mustard,  enamels,  etc., 
and  which  should  contain  no  iron.  The  axis  is  of 
hard  bronze  or  brass.  The  lime  should  be  ground 
long  enough  to  destroy  any  hard  and  coarse  portions, 
and,  as  a  further  security,  it  is  passed  through  a  very 
fine  copper  sieve. 

As  the  mixture  of  lime  and  copper  solution  must 
be  made  in  certain  proportions,  the  quantity  of  dry 
material  in  the  copper  liquor  and  in  the  milk  of  lime 
is  determined  by  drying  samples  of  them.  This  test 
is  made,  for  instance,  upon  1  litre  of  the  solution  of 
copper,  and  the  same  volume  of  milk  of  lime;  but 
the  latter  should  be  well  stirred  before  taking  the 
sample.  The  proportions  for  mixing  are  1  part  of 
well-dried  lime,  and  1.75  parts  of  dry  copper  salt.  We 
should  observe  that  the  quantity  of  lime  may  be  con- 
siderably increased  above  this  proportion  at  the  ex- 
pense, however,  of  a  lesser  intensity  in  the  coloration 
of  the  product.  The  proportions  which  we  have  just 
indicated  generally  furnish  the  finest  color.  In 
order  to  ascertain  whether  the  correct  amount  of  lime 
has  been  added,  a  sample  of  the  clear  liquor  above  the 
colored  precipitate  is  tried  with  ammonia,  which  should 
produce  but  a  faint  blue.  If  the  coloration  be  deep, 
more  milk  of  lime  is  added,  and  the  whole  is  thoroughly 
mixed. 


344 


MAOTFACTURE  OF  COLORS. 


When  the  precipitate  has  become  well  settled,  the 
clear  liquor  is  decanted,  and  the  color  is  carefully 
washed  with  pure  and  limpid  water.  It  is  then 
drained  upon  cloth  filters  until  it  has  acquired  a  cer- 
tain consistency,  and  forms  a  green  paste. 

For  the  subsequent  operations,  it  is  necessary  to 
determine  the  proportion  of  water  held  in  this  green 
paste,  in  order  to  compound  the  ingredients.  A  few 
grammes  are  slowly  and  cautiously  dried,  and  the 
loss  in  weight  indicates  the  proportion  of  water. 
This  paste  generally  loses  three-fourths  of  its  weight 
in  drying.  On  this  hypothesis  25  kilogrammes  of 
paste  are  stirred,  in  a  leaden  tub,  with  50  litres  of  pure 
water,  to  which  are  added  2.5  kilogrammes  of  the  wet 
lime,  which  are  immediately  stirred  without  loss  of 
time,  this  rapidity  being  an  essential  condition.  After- 
wards, 1.5  litres  of  a  solution  of  the  best  kind  of 
pearlash  potash,  marking  15°  Be.,  and  filtered  clear, 
are  added,  and  immediately  and  vigorously  stirred  in. 
The  mixture  is  then  carried,  without  loss  of  time,  to 
the  mill  already  mentioned,  in  which  it  is  ground  for 
a  long  time,  because  the  beauty  of  the  pigment  de- 
pends greatly  upon  a  homogeneous  mixture. 

On  the  other  hand,  for  the  50  litres  of  green  paste 
there  has  been  prepared  a  clear  solution  of  0.5  kilo- 
gramme of  pure  sal  ammoniac  in  10  litres  of  water, 
and  another  solution  of  1  kilogramme  of  sulphate  of 
copper  in  10  litres  of  water. 

The  liquid  paste  of  the  mill  is  then  drawn  into  a 
stoneware  jar,  and,  immediately  after,  the  two  solu- 
tions of  sal  ammoniac  and  sulphate  of  copper  are 
poured  in  at  the  same  time.  The  jar  is  closed  with  a 
good  cork,  which  is  held  tight  by  a  string,  and  luted 
over  with  a  mastic  of  tallow  and  rosin,  soft  enough  to 


BLUE  COLORS.  345 


yield  to  the  fingers.  The  jar  is  moved  in  every 
direction  and  shaken  as  much  as  possible. 

After  standing  for  four  or  five  days,  the  contents 
of  the  jar  are  poured  into  a  lead-lined  tub  of  a  capa- 
city of  about  250  litres.  Water  is  added  up  to  a  few 
centimetres  from  the  top,  the  whole  is  stirred,  then 
left  to  settle,  and  the  clear  liquid  decanted,  and  so 
on,  at  least  eight  times.  The  clear  water  of  the  last 
washing  is  tried  with  a  piece  of  turmeric  paper,  and, 
if  the  yellow  color  becomes  brown-red,  the  washing 
should  be  continued. 

The  deposit  thus  obtained  is  called,  in  England, 
verditer  in  paste.  The  greater  portion  of  that  manu- 
factured is  used  in  that  state  by  manufacturers  of 
paper  hangings.  For  other  arts,  and  for  exportation, 
the  paste  is  sloAvly  dried,  and  becomes  solid  and 
brittle. 

This  manufacture  requires  great  cleanliness,  well- 
ventilated  rooms,  no  sulphuretted  gases,  etc.  Pure 
waters  have  a  great  influence  on  the  beauty  of  the 
product. 

II.  A  skilful  manfacturing  chemist,  Mr.  L.  Gr. 
Gentele,  has  published,  in  the  Technologiste,  vol.  xvii. 
page  341,  the  results  of  researches  made  by  himself 
upon  the  preparation  of  several  copper  colors,  and 
especially  of  blue  ashes. 

"The  blue  colors,"  says  he,  "found  in  the  trade, 
and  prepared  especially  with  oxide  of  copper,  are : 
The  mountain  blue,  the  green-blue  of  Bremen,  and 
the  calcareous  blue,  or  blue  ashes  in  paste.  As  far 
as  I  know,  no  accurate  researches  on  the  latter  pro- 
duct have  been  published;  and  the  circumstances 
under  which  it  is  formed  are  so  peculiar,  that  I  suspect 
that  colors  made  in  a  similar  manner  may  be  com- 
pounds in  chemical  proportions. 


346 


MANUFACTURE  OF  COLORS. 


"  One  kind  of  blue  ashes  in  paste  is  obtained  by 
the  precipitation  of  sulphate  of  co^Dper  with  a  very 
thin  milk  of  lime  added  in  excess,  and  cold,  and  by 
thoroughly  washing  the  precipitate,  which  may  then 
be  dried  without  turning  black.  The  preparation  of 
another  kind  of  blue  ashes  in  paste,  resembling  moun- 
tain blue,  is  made  by  precipitating,  in  the  cold,  a 
solution  of  100  parts  of  sulphate  of  copper  and  12.5 
parts  of  sal  ammoniac  with  a  milk  of  lime  prepared 
from  30  parts  of  quicklime.  The  liquor  remains  blue 
for  a  few  days,  and  when  this  coloration  has  disap- 
peared the  pigment  is  made.  In  order  to  obtain  very 
pure  colors  the  lime  is  ground  after  having  been 
slaked,  and  the  milk  of  lime  formed  is  left  to  stand 
for  several  weeks  before  it  is  employed. 

"As  the  latter  color  is  not  obtained  without  sal 
ammoniac,  I  have  concluded  that  this  substance  is 
of  absolute  necessity  in  its  preparation.  I  have, 
therefore,  prepared  a  solution  of  ammoniacal  sulphate 
of  copper  with  excess  of  ammonia,  that  is,  I  have 
added  ammonia  in  sufficient  quantity  to  dissolve  the 
first  precipitate,  and  to  impart  a  strong  ammoniacal 
odor  to  the  solution,  which  was  filtered  afterwards  in 
order  to  separate  a  small  quantity  of  oxide  of  iron. 

"By  pouring,  drop  by  drop,  this  solution  into 
lime-water,  I  have  immediately  obtained  a  blue  pre- 
cipitate, and  the  liquor  took  a  bluish  coloration  only 
when  all  of  the  lime  was  combined.  The  precipitate 
formed  before  the  coloration  of  the  liquor  was  sepa- 
rated and  washed ;  then  a  portion  A  was  dried  and 
kept  to  be  analyzed. 

"  If,  on  the  other  hand,  the  milk  of  lime  be  poured, 
drop  by  drop,  into  the  ammoniacal  copper  solution, 
there  is  also  produced  a  precipitate,  which  by  stirring  is 


BLUE  COLORS. 


347 


completely  redissolved,  and  remains  so  for  a  long  time, 
when  the  liquor  is  tepid.  Lastly,  when  a  permanent 
precipitate  has  been  formed,  and  has  been  separated 
by  filtration,  the  liquor,  after  standing  for  several 
days,  deposits  crystals  of  a  magnificent  blue,  several 
centimetres  in  length,  but  no  thicker  than  a  hair, 
which  break  into  small  pieces  when  the  liquid  is 
stirred.  These  crystals  B  were  separated  in  order 
to  be  analyzed. 

"  The  compound  A  was  not  entirely  pure,  on  ac- 
count of  the  presence  of  a  small  proportion  of  carbon- 
ate of  lime,  formed  during  the  washings  and  drying. 
This  product  greatly  resembles  Bremen  blue,  except 
that  it  is  slightly  greenish,  flaky,  and  amorphous. 
Under  the  action  of  heat,  it  behaves  like  the  hydrated 
oxide  of  copper  of  the  Bremen  blue,  but  it  bears  a 
greater  elevation  of  temperature  before  it  becomes 
brown. 

"The  analysis  made  of  it  gave  as  result — 


Water   18.76 

Sulphuric  acid   1L20 

Oxide  of  copper   46.85 

Lime   16.19 

Loss  .       .    1.00 


100.00 

"  The  loss  consists  of  carbonic  acid.  The  propor- 
tion of  lime,  not  combined  with  sulphuric  acid,  re- 
quires 6.5  of  carbonic  acid.  Therefore  the  analysis 
becomes — 

(11.20  sulphuric  acid, 

X  1.84  lime, 

(  8.35  lime, 

(  6.50  carbonic  acid, 

46.85  oxide  of  copper, 

18.16  water. 


348 


MANUFACTURE  OF  COLORS. 


"  This  precipitate,  thoroughly  washed  in  pure  water, 
became  very  soluble  in  ammonia,  whereas,  previous 
to  the  washings,  it  was  insoluble.  We  should  there- 
fore suppose  that  this  precipitate,  before  being  dried 
and  washed,  holds  a  combination  of  lime,  which, 
during  the  drying  operation,  combines  with  carbonic 
acid,  and  sets  at  liberty  the  hydrated  oxide  of  copper. 
As  the  washings  carry  away  the  sulphate  of  lime,  it 
is  difficult  to  decide  upon  the  composition  of  the 
precipitate. 

"  The  compound  B  may  be  obtained  pure  in  the 
shape  of  crystals,  or  rathei*  of  a  crystaUine  precipi- 
tate. It  is  generally  impure  in  commercial  blue 
ashes  in  paste.  This  blue  is  very  bright,  and  resists 
the  action  of  the  air  well.  The  thicker  crystals  possess 
the  blue  color  of  mountain  blue,  although  slightly 
lighter  in  tone.  Heated,  these  crystals  acquire  a 
brown  color,  of  a  glassy  brightness.  They  are  in- 
soluble in  water,  but  very  soluble  in  the  sulphate  of 
ammonia. 

"  Their  analysis  gives  the  following  composition  : — 

Lime   16.19 

Oxide  of  copper   33.56  33.44 

Sulphuric  acid   23.83 

Water   26.01  27.00 

99.59 

"  This  compound  is  not  obtained  by  digesting  sul- 
phate of  lime  with  ammoniacal  sulphate  of  copper 
containing  an  excess  of  ammonia. 

"From  the  behavior  of  caustic  lime  with  ammo- 
niacal sulphate  of  copper,  and  also  from  the  diflPerences 
presented  by  the  two  precipitates,  we  may  establish 
rules  for  the  method  of  preparing  this  color,  and 
foresee  the  circumstances  which  will  influence  its 


BLUE  COLORS. 


349 


good  or  bad  quality.  For  instance,  the  compound  B 
is  not  formed,  when  the  proportion  of  lime  is  such  as 
to  precipitate  entirely  the  sulphuric  acid  of  the  sul- 
phate of  copper.  Out  of  7  atoms  of  sulphate  of 
copper  in  the  liquor,  5  are  precipitated  by  hydrated 
lime,  and  the  last  two  are  decomposed  by  ammonia. 
A  greater  proportion  of  lime  will  produce  a  precipi- 
tate holding  a  certain  quantity  of  the  compound  A, 
which  is  less  valuable,  and  impairs  the  quality  of  the 
color.  A  smaller  proportion  of  lime  renders  the 
color  finer  and  more  crystalline,  because  it  crj^stal- 
lizes  partly  in  the  excess  of  solution.  It  is  therefore 
possible,  by  an  incomplete  decomposition  and  a  smaller 
yield,  to  obtain  a  finer  and  more  crystalline  color. 

"  If  we  calculate  the  proportions  necessary  for  the 
formation  of  the  color,  we  have — 

t  equivalents  of  sulphate  of  copper ; 
2  "  ammonia; 

5  "  lime. 

And  if,  instead  of  2  equivalents  of  ammonia,  we 
take  2  equivalents  of  sal  ammoniac  and  2  of  lime,  the 
weights  become — 

100  parts  of  sulphate  of  copper; 
24     "  lime; 
22.5  "     "  sal  ammoniac, 

which  proportions  will  furnish  the  purest  color. 

"  Examination  has  also  been  made  as  to  how  a  solu- 
tion of  ammoniacal  sulphate  of  copper,  with  excess  of 
ammonia,  behaves  with  caustic  potassa  or  soda.  Either 
of  these  alkalies  produces  in  this  solution  a  fine  blue 
precipitate,  but  the  liquor  does  not  become  decolor- 
ized, except  by  evaporating  the  ammonia.  By  wash- 
ing this  precipitate,  its  color  becomes  lighter  and 
.lighter,  and  finally  resembles  that  of  Bremen  blue. 


350 


MAXUFACTURE  OF  COLORS. 


It  is  composed  of  hydrated  oxide  of  copper,  but  it 
contains  also  a  small  proportion  of  carbonic  acid. 

"  It  is  a  remarkable  fact  that  this  precipitate,  even 
when  heated  in  the  presence  of  a  great  excess  of 
potassa  or  soda,  does  not  become  brown,  as  is  the  case 
when  a  solution  of  sulphate  of  copper  is  precipitated 
by  a  slight  excess  of  these  bases. 

"  The  presence  of  ammonia  renders  the  hydrated 
oxide  of  copper  much  more  durable.  This  circum- 
stance explains  a  useful  manipulation  in  the  prepara- 
tion of  Bremen  blue.  Indeed,  if,  for  changing  to  a 
blue  the  precipitate  obtained  from  a  copper  salt  by  an 
alkali  which  is  not  entirely  caustic,  we  employ  a 
caustic  lye  of  potassa  with  an  addition  of  ammonia  or 
of  sal  ammoniac,  we  are  much  more  certain  of  success, 
because  a  passage  to  a  black  color,  which  is  to  be 
feared,  does  not  then  occur  even  with  a  great  excess 
of  caustic  potassa  lye." 

III.  Since  blue  ashes  are  manufactured  in  England 
better  than  in  France,  it  is  necessary  to  be  able  to 
distinguish  one  from  the  other.  The  following  pro- 
cess has  been  proposed : — 

When  the  blue  ashes  are  in  paste,  a  sample  is 
thoroughly  dried  at  a  low  temperature,  and  then 
heated  in  a  glass  tube  with  a  small  quantity  of  fused 
caustic  potassa  or  soda.  The  French  blue  ashes 
disengage  ammonia,  easily  recognized  by  its  smell, 
while  the  English  product  does  not  present  the  same 
phenomenon. 

The  English  blue  ashes,  the  manufacture  of  which 
is  still  kept  a  secret,  are  a  carbonate  of  copper  of  a 
rather  dark  blue,  but  less  pure  in  color  than  the 
hydrated  oxide  of  copper  of  Mr.  Peligot. 

IV.  The  natural  color,  called  mountain  hlue^  azurite^ 


BLUE  COLORS. 


351 


and  Armenian  stone,  is  a  basic  carbonate  of  copper, 
found  in  quartz  rocks  in  Siberia,  the  Tyrol,  Bohemia, 
Saxony,  Hesse,  England,  and  France.  This  substance 
is  rare  and  expensive,  and  possesses  a  very  rich  sky- 
blue  color,  of  which  blue  ashes  are  an  imitation. 
The  native  product  is  always  more  durable  than  the 
artificial  one. 

§  13.  Smalt 

Smalt,  which  is  also  known  under  the  names  of 
azure  blue,  smalt  hlue,  zaffer  hlue,  Saxony  hlue,  enamel 
blue,  starch  blue,  cobalt  glass,  etc.,  appears  to  be, 
according  to  Mr.  Ludwig,  a  double  silicate  of  potassa 
and  cobalt,  mixed  with  variable  quantities  of  lime, 
alumina,  magnesia,  oxide  of  iron,  oxide  of  nickel,  and 
sometimes  of  arsenic  and  carbonic  acid,  and  water. 
The  intensity  of  the  color,  in  the  opinion  of  the  same 
chemist,  depends  on  the  greater  or  less  proportion  of 
the  double  silicate. 

The  crude  materials  employed  in  the  manufacture 
of  smalt  are,  cobalt  ore,  sand,  and  potassa.  The  min- 
eral generally  used  in  Saxony,  where  this  color  is 
prepared  the  best,  is  a  speiss  or  arsenide  of  cobalt  and 
iron. 

The  broken  ore  is  roasted  at  a  red  heat  in  a  rever- 
beratory  furnace,  which  has  a  very  high  stack  for  car- 
rying far  up  into  the  air  the  arsenical  and  sulphurous 
fumes.  When  vapors  cease  to  be  disengaged,  and 
when  the  material  begins  to  be  pasty,  the  roasted 
product  is  removed  from  the  fire,  cooled,  pulverized, 
and  passed  through  a  silk  sieve.  This  powder  is 
called  zaffer, 

A  pure  sand  free  from  iron,  mica,  talc,  or  lime,  is 
also  calcined  and  thrown  into  cold  water,  while  still 


352 


MANUFACTURE  OF  COLORS. 


red-hot.  It  is  then  powdered,  washed  with  hydro- 
chloric acid,  and  dried. 

The  potassa  should  he  pure,  and  contain  no  lime, 
sand,  or  chloride  of  sodium. 

It  is  difficult  to  indicate  heforehand  the  propor- 
tions for  the  mixture,  because  we  must  be  guided  by 
the  nature  of  the  cobalt  ore,  or  by  the  quality,  or  by 
the  tone  of  color  which  is  to  be  produced.  The  cobalt 
and  sand  are  first  added,  and  then  the  potassa ;  the 
whole  is  introduced  into  clay  pots  having  each  a  hole 
in  the  bottom,  which  may  be  closed.  The  pots  are 
then  placed  in  a  glass  furnace  heated  by  a  wood  fire. 
After  four,  five,  or  six  hours  of  calcination,  the  mate- 
rial is  melted,  and  forms  three  layers ;  the  upper  one, 
or  dross,  is  composed  of  sulphate  and  arseniate  of 
potassa,  and  chloride  of  potassium  ;  the  lowest  one  is 
composed  of  ore  and  of  unmelted  substances,  and  the 
intermediary  one  is  the  blue  glass. 

The  greater  part  of  the  dross  is  taken  off  with 
hot  iron  ladles,  and  the  lowest  layer  of  unmelted 
materials  is  removed  through  the  bottom  hole.  After 
this  hole  has  been  closed  again,  the  melted  blue 
glass  is  ladled  out  into  basins  filled  with  cold  water. 
The  pots  are  charged  again,  and  a  new  operation 
begins. 

The  glass  is  removed  from  the  water,  dried,  and 
pulverized  under  horizontal  stones.  The  powder  is 
then  levigated  (floated),  in  order  to  obtain  various 
degrees  of  fineness,  which  are  designated  by  the 
names  of  smalt  of  the  first,  second,  third,  and  fourth 
fire,  or  by  other  marks  distinctive  of  their  color  or 
degree  of  comminution. 

Independently  of  the  ordinary  smalt,  there  is  another 
darker  blue,  with  a  very  fine  grain,  and  which  is  gen- 


BLUE  COLORS. 


353 


erallj^  called  Escliel  hhie  or  Laundry  blue.  It  is  ob- 
tained by  mixing  finely  powdered  zaffer  with  a  smalt 
of  good  quality.  It  is  distinguished  from  the  real 
smalt  by  stirring  it  in  water ;  after  a  few  seconds,  the 
zaffer  is  precipitated,  whilst  the  smalt  remains  in  sus- 
pension in  the  liquid. 

In  order  to  obtain  a  smalt,  of  a  magnificent  blue,  it 
should  be  prepared  with  a  pure  oxide  of  cobalt.  The 
ore  is  finely  ground,  and  treated  by  boiling  nitric  acid, 
which  makes  nitrates  of  cobalt  and  of  iron,  and  arsenic 
acid.  The  liquor  is  decanted,  diluted  with  water,  and 
decomposed  by  a  solution  of  carbonate  of  soda.  There 
is  produced  a  soluble  arseniate  of  soda,  and  a  precipi- 
tate of  the  carbonates  of  cobalt  and  iron,  which  is 
collected,  carefully  washed,  dried,  and  then  calcined. 
The  resulting  oxide  of  cobalt,  holding  a  small  propor- 
tion of  oxide  of  iron,  is  mixed  with  sand  and  potassa. 

The  smalts  of  Saxony,  most  generally  found  in  the 
market,  are  marked  with  the  following  letters,  of 
which  F,  M,  and  O  indicate  the  proportion  of  cobalt, 
and  C,  CB  the  degree  of  fineness  of  the  grain : — 

H,  Common  smalt. 

E,  Eschel  variety. 

B,  Bohemian  smalt. 

CF,  Fundamental  color. 

FC,  Fine  color. 

FCB,  Fine  color  from  Bohemia. 

FE,  Fine  Eschel. 

MC,  Medium  color. 

MCB,  Medium  color  from  Bohemia. 

ME,  Medium  Eschel. 

OC,  Ordinary  color. 

OCB,  Ordinary  color  from  Bohemia. 

OE,  Ordinary  Eschel. 

In  order  to  indicate  a  smalt  which  contains  more 
cobalt  than  F,  several  F's  are  added ;  thus  FFFC  is 
23 


354 


MANUFACTURE  OF  COLORS. 


of  a  higher  price  than  FFC,  and  this  is  more  valu- 
able than  FC.  On  the  other  hand,  if  the  blue  con- 
tains less  cobalt  than  OC,  ordinary  color,  a  number 
is  employed  ;  thus  OC^,  0C\  indicate  that  the  smalt 
contains  one-half  or  one-third  of  the  cobalt  of  the 
ordinary  quality. 

If  azure  blue  be  employed  for  inside  painting,  it 
has  the  inconvenience  of  turning  green  and  black ; 
moreover,  the  difficulty  of  grinding  it  fine  enough 
prevents  its  employment  for  artistic  painting.  Its 
principal  use  is  for  giving  an  azure  color  to  signs,  for 
instance,  which  are  painted  with  ordinary  blue  oil 
paint,  and  then  dusted  over  with  the  smalt.  It 
changes  less  in  size  than  in  oil,  and  on  that  account 
is  much  used  in  fresco  painting.    It  dries  rapidly. 

§  14.  Cceruleum, 

Coeruleum  is  a  new  blue  color  for  oil  and  water 
painting,  which  is  due  to  the  English  house  of  G. 
Eowney  &  Co.  It  is  a  light  blue,  slightly  greenish, 
and  does  not  appear  violet  under  artificial  light.  It 
covers  very  well,  it  is  not  granular,  and  is  especially 
well  suited  for  painting  a  transparent  sky  blue. 

Coeruleum  is  not  altered  by  solar  light  or  an  im- 
pure atmosphere,  and  caustic  alkalies  and  strong  acids 
are  without  action  upon  it  at  the  ordinary  tempera- 
ture. According  to  Mr.  S.  Bleekrode,  it  belongs  to 
the  colors  with  a  basis  of  cobalt  oxide,  although  it  is 
distinct  from  the  silicate  of  cobalt  and  potassa  or 
soda,  as  Mr.  Ludwig  calls  smalt  blue,  or  from  the 
aluminate  of  cobalt  of  Gahn,  the  cobalt  ultramarine 
of  Binder,  and  the  phosphate  of  alumina  and  cobalt 
of  Th^nard. 

Coeruleum  is  entirely  soluble  in  hot  hydrochloric 


BLUE  COLORS. 


355 


acid,  and  the  light-blue  coloration  of  the  solution  be- 
comes a  violet  red  when  it  is  diluted  with  water. 
The  primitive  color  reappears  by  concentration,  and 
the  pigment  is  restored  if  the  solution  be  evaporated 
to  dryness.  Nitric  acid  dissolves  the  cobalt  and 
leaves  a  white  residue,  which  is  mostly  composed  of 
stannic  acid.  The  green  coloration  of  this  solution 
shows  the  presence  of  a  small  proportion  of  iron  and 
nickel.  Concentrated  sulphuric  acid  does  not  dis- 
solve coeruleum ;  but  the  same  acid,  diluted  with  4 
volumes  of  water,  produces  a  partial  decomposition. 
Acetic  acid  and  caustic  potassa  do  not  act  upon  it  at 
the  temperature  of  ebullition. 

Coeruleum  is  principally  a  combination  of  an  oxide 
of  tin  with  the  oxide  of  cobalt.  The  greenish-blue 
reaction  by  which  oxide  of  tin  is  recognized  with  the 
blowpipe  is  generally  known.  Berzelius  mentions  a 
stannate  of  cobalt,  which  he  prepares  by  adding  a 
solution  of  stannate  of  potassa  to  one  of  cobalt. 
The  bluish  precipitate  thus  formed  becomes  of  a  light- 
red  color  after  washing,  and  then  brown.  If  it  be 
calcined  at  a  white  heat,  its  color  is  changed  into  a 
light  blue. 

The  composition  of  coeruleum  is — 

Oxide  of  tin  (stannic  acid)    ....  49.66 

Oxide  of  cobalt  18.66 

Sulphate  of  lime  and  silica    ....  31.68 

100.00 

The  stannate  of  cobalt  of  formula  SnO^CoO  re- 
quires 75  parts  of  stannic  acid,  and  37.5  parts  of  ox- 
ide of  cobalt ;  the  ratio  is  therefore  as  2:1.  The 
formula  of  coeruleum  is,  therefore,  3(SnO^CoO)  -|- 


356 


MANUFACTURE  OF  COLORS. 


SnO^,  that  is,  a  stannate  of  cobalt  mixed  with  stannic 
acid  and  sulphate  of  lime. 

It  is  said  that  there  is  in  the  market  an  imitation 
of  coernlenm,  prepared  by  mixing  French  ultramarine 
with  a  small  proportion  of  2^aples  yellow  and  white 
lead. 

§  15.  Litmus, 

This  coloring  substance  is  manufactured  in  Au- 
vergne,  Dauphine,  Holland,  etc.,  from  several  lichens, 
especially  the  Yariolaria  orcina  of  Achard.  The  pro- 
cess consists  in  grinding  them,  and  making  a  paste 
with  urine  and  half  of  their  weight  of  crude  potash. 
Care  is  taken  to  replace  the  evaporated  urine.  After 
40  days  of  putrefaction  the  mixture  acquires  a  purple 
color.  It  is  then  put  into  another  trough,  with  urine, 
and  the  blue  color  is  developed.  The  paste  is  after- 
wards mixed  with  lime  and  urine.  The  last  prepara- 
tion consists  in  giving  a  certain  consistency  to  the 
paste,  by  the  addition  of  carbonate  of  lime,  and 
moulding  the  mixture  into  small  cubes,  which  are 
dried. 

Litmus  is  used  only  in  distemper  painting,  or  for 
giving  an  azure  color  to  ceilings.  It  is  often  pre- 
ferred for  violet  and  lilac  body  grounds,  on  account 
of  its  hue.  This  color  is  not  durable,  and  becomes 
red  by  the  action  of  acids.  It  becomes  violet  with 
glue  size,  and  black  with  oil. 

§  16.  English  sky  hlue. 

Although  this  blue  has  little  to  do  with  painting, 
we  think  that  the  two  following  processes  may  be 
profitably  given,  since  the  products  are  largely  used 
in  the  household,  and  manufacturers  of  colors  should 


BLUE  COLORS. 


357 


know  how  to  prepare  them.  The  following  formula 
has  been  given  by  W.  Story :  Take  a  large  glass 
vessel,  or  an  iron  kettle  (but  in  the  latter  case  it  is 
not  necessary  to  use  iron  filings),  and  put  into  it  1 
kilogramme  of  fine  indigo  in  powder,  and  3  kilo- 
grammes of  sulphuric  acid  at  66°  Be. ;  stir,  and  let 
stand  for  24  hours,  at  most. 

On  the  other  hand,  dissolve  10  kilogrammes  of 
potash  in  20  litres  of  water,  and  pour  2  litres  of  this 
solution  into  the  indigo  mixture,  and  stir  well.  After- 
wards add  1  kilogramme  of  finely-cut  blue  (Castile) 
soap,  stir  continually,  and  add  the  solution  of  potassa 
until  the  whole  appears  as  a  dry  powder(?).  Pour  on 
then  1  litre  of  pure  water  and  the  remainder  of  the 
potash  solution.  Lastly,  mix  0.5  kilogramme  of  finely 
powdered  alum.  After  standing  for  three  days,  the 
mixture  is  made  into  balls,  which  are  dried  in  the  air, 
and  employed  for  bluing  linens. 


Balls  of  Wuy. 

Indigo  1  kilogramme. 

Sulphuric  acid  at  67°  Be.    ...     6  kilogrammes. 

White  potash  15  " 

White  soap  1  kilogramme. 

Quicklime  100  grammes. 

Common  salt       .       .       .       .       .100  " 


The  powdered  indigo  is  purified  in  10  litres  of  al- 
cohol, then  in  dilute  hydrochloric  acid,  and  after 
drying  in  the  shade  or  in  a  moderately  hot  stove-room, 
is  ground  again  very  fine.  It  is  then  dissolved  in 
sulphuric  acid,  and  the  solution  is  poured  into  a  lead- 
lined  vessel,  in  which  the  other  ingredients  are 
added.  When  the  paste  is  thick  enough  it  is  moulded 
into  balls. 


i 


358 


MANUFACTURE  OF  COLORS. 


SECTION  III. 

YELLOW  COLORS. 

Yellows  in  general, — Yellow  pigments  are  derived 
from  many  substances,  some  of  them  being  natural, 
and  the  others  artificial  products.  It  is  to  be  re- 
gretted that  the  light  and  bright  tones  of  yellow  are 
often  wanting  in  fastness  and  durability.  Iron,  anti- 
mony, lead,  chromium,  arsenic,  cadmium,  and  several 
vegetable  substances,  such  as  weld,  quercitron  bark, 
Persian  and  Avignon  berries,  yellow  wood,  curcuma, 
saffron,  and  ahoua,  are  the  raw  materials  used  at  the 
present  time  for  the  manufacture  of  yellows.  Telloiv 
ochre,  Hut  ochre,  raw  Italian  earth,  raw  Sienna  earth, 
and  Mars  yellow  are  iron  compounds.  JS^apIes  yellow, 
mineral  yellow,  chrome  yellow,  Cologne  yellow.  Turner 
yellow,  mineral  gamboge,  antimony  yellow,  orpin, 
^massicot,  etc.,  are  artificial  colors  manufactured  from 
antimony,  lead,  chromium,  and  arsenic.  Lastly, 
Avignon  herries,  terra-merita,  saffron  yellow,  stil  de 
grain,  and  weld  yellows,  those  from  quercitron  barh, 
and  yellow  wood,  are  extracted  from  various  vegetable 
substances. 

§  1.  Ochres, 

This  is  the  name  given  to  various  clays,  the  paste 
of  which  is  more  or  less  fine,  smooth,  opaque,  dull, 
easily  broken,  adhering  to  the  tongue,  and,  when  wet, 
emitting  a  peculiar  clayish  smell.  Those  of  good 
quality  are  greasy  to  the  touch  and  are  easily  ground. 
On  the  other  hand,  those  which  are  dry  and  sandy 
are  more  difficult  to  grind,  and  are,  therefore,  less 
esteemed. 

Ochres  are  colored  brown,  yellow,  red,  and  reddish- 

^  ■ 


YELLOW  COLORS. 


359 


yellow;  nevertheless  we  put  them  together  under 
the  same  head,  because,  by  calcination,  they  all  be- 
come red  or  hrown.  The  good  qualities  of  ochres 
are  in  direct  ratio  with  the  number  of  washings  or 
floatings  they  have  been  submitted  to.  Their  color 
is  due  to  the  oxides  of  iron  they  contain.  In  fact, 
ochres  are  compounds  of  clay  and  oxide  of  iron. 

Yellow  ochre^  more  or  less  pure,  is  a  true  yellow, 
but  earthy  looking.  There  are  many  varieties  of  it, 
and  it  will  be  sufl&cient  to  give  as  examples  the  two 
following,  which  are  well  fitted  for  painting. 

I.  Ochre  from  Saint- Oeorges-sur-la- Free  (Cher). 


It  is  composed  of — 

Clay   69.5 

Peroxide  of  iron   23.5 

Water   T.O 


100.0 

It  is  of  a  handsome  yellow,  of  very  fine  grain. 

II.  Ochre  from  la  Berjaterie  (^sTievi'e).  Its  compo- 
sition is — 

Clay  64.4 

Peroxide  of  iron  26.6 

Water  9.0 

100,0 

Its  color  is  as  deep  as  the  preceding  one,  but  not 
so  finely  granulated.  Very  good  ochres  are  also 
extracted  from  Pourrain,  Diges,  and  Toucy  (Yonne). 

When  yellow  ochre  is  calcined,  water  escapes,  and 
the  substance  becomes  red.    It  is  then  red  ochre. 

For  removing  the  water  from  the  hydrated  oxide 
of  iron,  and,  at  the  same  time,  causing  the  red  colora- 
tion to  appear,  the  yellow  ochre  is  broken  into  small 
pieces  which  are  calcined  upon  a  plate  of  cast-iron, 
heated  from  below.    When  the  substance  has  ac- 


360 


MANUFACTURE  OF  COLORS. 


quired  the  desired  tone  of  color,  it  is  quickly  cooled 
by  being  thrown  into  water.  After  several  washings 
the  deposit  is  dried  in  the  open  air.  The  greater  the 
proportion  of  iron,  the  brighter  the  ochre;  but  we 
must  suppose  that  the  clay  contains  no  organic  sub- 
stances capable  of  reducing  the  metal. 

Ochres  are  not  generally  sold  as  they  are  extracted 
from  their  beds,  but  are  dried  in  the  sun,  pulverized, 
and  sifted  to  a  greater  or  less  degree  of  fineness  as 
desired  by  the  trade.  For  still  finer  ochres,  they  are 
ground  in  a  mill,  and  floated  in  large  cisterns.  The 
longer  the  time  required  for  the  ochre  to  subside,  the 
finer  its  quality.  The  deposits  are  collected,  dried 
in  the  sun,  and  sold  powdered  or  in  lumps. 

It  has  been  attempted  to  manufacture  ochres  of 
various  degrees  of  fineness,  by  submitting  the  powder 
to  a  powerful  blast  of  air  in  rooms  or  troughs  of  great 
size.  The  greater  the  comminution,  the  greater  the 
distance  the  powder  is  carried  away.  By  collecting 
the  products  in  the  order  in  which  they  have  settled, 
we  obtain  ochres  of  every  degree  of  fineness. 

The  yellow  ochres  are  generally  sold  in  powder  or 
in  lumps;  but  the  red  ochres,  called  Prussian  red, 
hrown-red,  red  earth,  and  Nuremberg  red,  are  sold 
in  the  powdered  state,  whereas  the  retailers  deliver 
them  in  the  form  of  paste.  It  is  sufficient  to  grind 
the  red  ochres  with  a  small  proportion  of  water  and 
of  chloride  of  calcium.  This  salt,  on  account  of  its 
hygrometric  properties,  maintains  a  certain  dampness 
in  the  paste. 

Mr.  Cochois  calcines  his  ochres  in  perfectly  tight 
ovens,  or  in  closed  iron  vessels.  The  product  is  then 
washed  for  the  purpose  of  removing  the  foreign  sub- 
stances. The  tones  and  hues  may  be  varied  at  will 
by  calcination. 


YELLOW  COLORS. 


361 


Mr.  de  Hostaing,  as  we  have  already  seen  in  the 
articles  on  white  lead,  has  invented  a  process  for 
pulverizing  fused  metals  by  centrifugal  force.  With 
cast-iron,  it  seems  possible  to  produce  very  cheaply 
oxides  and  iron  colors  for  painting.  But  this  process 
has  not  been  applied  on  a  large  scale. 

Pure  yellow  ochre  with  glue  size,  or  oil,  acquires 
the  color  of  gingerbread,  and  is  used  for  painting 
stone  floors.  Mixed  with  red  ochre  and  a  white  pig- 
ment, it  produces  the  various  tones  of  wood  and  stone. 
The  mixture  with  black  is  olive-green. 

§  2.  Rut  (rivulet)  ochre. 

This  ochre  is  a  hydrate  of  sesquioxide  of  iron, 
mixed  with  clay  and  silica.  It  is  generally  found  in 
the  rivulets  in  the  vicinity  of  iron  mines.  Its  color 
is  brownish-yellow,  and  it  forms  earthy  and  pulveru- 
lent masses.  Its  tone  becomes  darker  with  glue  size, 
and  with  oil  it  resembles  chocolate.  Mixed  with 
from  10  to  12  times  its  own  weight  of  white  lead,  it 
has  the  color  of  oak  wood. 

This  ochre  is  composed  of — 

Sesquioxide  of  iron  83 

Silica     .       .       .       .       .       .       .  .5 

Water   .  12 

100 

§  3.  Italian  and  Sienna  earths. 

Italian  earth  resembles  in  tone  of  color  Rut  ochre, 
but  is  brighter.  On  the  other  hand.  Sienna  earth  is 
neither  so  bright  nor  so  fast ;  indeed  it  is  more  easily 
changed  by  many  foreign  substances.  In  their  raw 
state,  these  earths  are  brown-yellow  with  an  orange 
tinge  J  calcined,  they  are  of  a  fine  brown-red.  All 


362 


MANUFACTURE  OF  COLORS. 


these  natural  raw  ochres,  used  for  ordinary  and  dis- 
temper painting,  necessitate  no  other  preparation  but 
their  thorough  washing  and  floating  in  water  in  order 
to  allow  the  foreign  substances  to  settle  down  and 
be  separated.  The  washed  pigment  is  collected  upon 
paper  filters  held  upon  stretched  cloths,  and  when  it 
has  become  sufficiently  dry,  it  is  formed  into  troches 
which  are  completely  dried  npon  other  gray  blotting 
papers. 

§  4.  'Ve7uce  red,    Antwerp  red.    Terra  rosa. 

There  are  to  be  found  in  the  trade,  under  the  names 
of  Venice  red,  Antwerp  red,  and  terra  rosa,  other 
ochres  which  have  very  likely  been  prepared  in  the 
same  manner  as  ordinary  red  and  yellow  ochres. 

Venice  red  is  a  splendid  red  ochre  which  comes 
from  Italy ;  but  its  preparation  and  the  exact  place 
from  which  it  is  extracted,  are  not  well  known. 

Antwerp  red  is  a  fine  ochre  which  is  exported  from 
Flanders. 

Lastly,  terra  rosa  is  an  Italian  ochre,  which  is  lilac- 
red  when  in  powder,  and  deep  red  when  ground  in 
oil.  It  would  be  extensively  used  in  the  arts  were 
it  better  known,  and  to  be  had  in  larger  quantities. 

§  5.  Mars  yellows. 

Whatever  be  the  care  taken  in  the  preparation  of 
ochres,  they  always  have  an  earthy  look,  which  pre- 
vents them  from  being  used  in  fine  painting.^  The 
effort  has  been  made  in  the  arts  to  manufacture  a 
product  having  the  same  durability  as  ochres,  but 
purer,  and  of  a  brighter  color.  The  best  known  pro- 
cess for  this  purpose  is  that  of  Mr.  Bourgeois,  and 
is  as  follows : — 


YELLOW  COLORS. 


363 


Sulphate  of  iron  is  prepared  by  dissolving  an  ex- 
cess of  clean  wrought  iron  in  sulphuric  acid  diluted 
with  4  or  5  parts  of  water.  The  crystallized  sulphate 
is  dissolved  in  pure  water,  and  an  equal  quantity  of  a 
solution  of  alum  is  mixed  with  it,  and  poured  into  a 
pine  tub  to  about  1  centimetre  above  the  bottom.  The 
tub  is  then  filled  with  pure  water  which  has  not  been 
filtered  upon  charcoal,  because  it  may  contain  car- 
bonic acid,  which  will  alter  the  oxide  of  iron.  The 
mixture  is  precipitated  by  a  solution  of  American 
potash.  After  a  thorough  stirring  and  settling  for 
24  hours,  the  water  is  decanted,  and  the  precipitate 
collected  with  a  wooden  spatula.  After  draining 
upon  paper,  the  deposit  is  formed  into  troches,  which 
are  allowed  to  dry  upon  blotting  paper. 

This  preparation,  which  is  supposed  to  be  a  mix- 
ture of  hydrated  oxide  of  iron,  carbonate  of  iron,  and 
alumina  in  variable  proportions,  is  of  a  fine  gold- 
brown  yellow.  If  it  be  calcined  at  different  tempera- 
tures, and  under  particular  conditions  which  are  held 
secret,  the  product  is  an  iron  or  Mars  violet,  red, 
brown,  and  orange.  It  is  probable  that  during  these 
operations  the  oxide  of  iron,  mixed  with  alumina, 
becomes  more  or  less  peroxidized  and  dehydrated. 

As  the  Mars  yellow  is  quite  expensive,  and  requires 
a  great  deal  of  practice  for  its  successful  manufac- 
ture, the  efibrt  has  been  made  to  substitute  other 
preparations  for  it,  such  as  a  mixture  of  sulphate  of 
lime  and  oxide  of  iron  made  as  follows : — 

One  kilogramme  of  protosulphate  of  iron  (green 
copperas)  is  dissolved  in  20  litres  of  water,  and  into 
this  solution  is  poured  a  sifted  milk  of  lime,  prepared 
by  diluting  in  40  litres  of  cold  water  one  kilogramme 
of  very  white  quicklime.    A  green  precipitate  is 


364 


MANUFACTURE  OF  COLORS. 


thus  formed,  which  is  washed  several  times  with  cold 
water,  and  then  exposed  to  the  air.  It  soon  becomes 
peroxidized,  and  acquires  a  yellow  tinge. 

A  reddish-yellow  is  also  prepared  by  precipitating 
a  solution  of  sulphate  of  sesquioxide  of  iron  with 
carbonate  of  soda.  The  deposit  of  hydrated  sesqui- 
oxide is  washed,  but  its  color  is  never  pure.  Part  of 
the  reddish  tinge  may  be  removed  by  adding  a  small 
proportion  of  alum. 

The  artificial  ochre  (oxide  of  iron  and  alumina)  is 
a  good  substitute  for  the  natural  ochres ;  it  is  of  a 
gold  brown-yellow,  and,  when  mixed  with  white  lead, 
many  tones  and  hues  may  be  obtained,  which  are  very 
fine  and  durable. 

The  various  tones  and  hues  of  natural  ochres  are 
due  to  foreign  matters,  which  it  is  very  difficult  and 
expensive  to  separate.  On  the  contrary,  the  combina- 
tions of  Mars  yellow  with  other  fast  colors  allow  of 
the  production  of  all  the  desired  colors  and  hues, 
which  possess  great  durability. 

^  6.  Curcuma  or  terra  merita. 

This  root  is  also  known  under  the  names  of  Souchet, 
Indian  saffron,  Curcuma  rotunda,  and  C,  long  a  (Lin.), 
according  as  it  is  round  or  elongated.  These  two  kinds 
come  from  the  East  Indies,  and  differ  but  slightly. 
The  elongated  one  is  more  commonly  found  in  the 
trade,  and  is  cylindrical,  twisted,  nearly  as  thick  as 
the  little  finger,  and  orange-yellow  inside.  Its  frac- 
ture resembles  wax,  the  thin  envelope  is  like  shagreen, 
its  taste  is  hot  and  bitter,  and  the  smell  is  analogous 
to  that  of  ginger. 

The  round  curcuma  forms  ovoid  tubercles,  nearly 
as  big  as  English  walnuts,  and,  when  newly  gathered, 


YELLOW  COLORS. 


365 


united  with  filaments.  The  envelope  is  gray,  and 
presents  many  circular  rings.  The  properties  of  this 
curcuma  are  the  same  as  those  of  the  preceding  one. 
Berthollet  once  examined  a  sample  of  curcuma  from 
Tabago,  and  found  it  superior  to  that  generally  met 
in  the  trade,  not  only  as  to  the  size  of  its  roots,  but 
also  in  the  greater  proportion  of  its  coloring  principle. 

This  substance  is  of  a  deep  color,  and  no  other 
yellow  is  brighter,  but  it  is  not  lasting  (fast).  Com- 
mon salt  and  sal  ammoniac  are  the  best  mordants  to 
fix  this  color,  although  they  darken  it-  towards  a 
brown.  A  small  proportion  of  hydrochloric  acid  is 
also  recommended.  The  best  roots  are  very  fragrant, 
heavy,  compact,  and  saffron-yellow.  Their  quality  is 
best  judged  when  fresh  and  whole,  although  they  are 
employed  dry  and  powdered.  Painters  use  curcuma 
for  painting  floors. 

From  an  analysis  by  Vogel  and  Pelletier,  the  com- 
position of  curcuma  is — 

Yellow  coloring  matter,  or  curcumin, 

Brown       "  " 

Substance  analogous  to  extracts, 

Lignin, 

Amylaceous  fecula, 
Gum  in  small  proportions, 
Bitter  and  fragrant  volatile  oil, 
Chloride  of  sodium. 

It  is  with  ether  that  is  extracted  the  neutral  sub- 
stance of  a  splendid  yellow  color,  although  not  very 
fast,  which  is  called  curcumin. 

In  order  to  give  more  durability  and  greater  depth 
to  the  orange-yellow  color  of  curcuma,  it  is  often 
mixed  with  Avignon  berries  and  carthamus. 


366  MANUFACTURE  OF  COLORS. 


§  7.  Stil-de-grain. 

.  Stil-de-grain  is  a  lake  prepared  with  the  buckthorn 
of  the  dyers  {Bhamnus  infectorius^  Lin.),  the  berries 
of  which  contain  a  yellow  coloring  substance,  called 
rhamnin,  which  turns  deep  yellow  with  alum,  and 
yellowish-brown  with  alkaline  carbonates. 

The  berries  of  the  buckthorn  which  grows  at 
Avignon,  in  France,  are  called  Avignon  hemes  even 
in  Spain  and  Italy.  They  are  generally  preferred  on 
account  of  their  cheapness,  although  the  proportion 
of  coloring  principle  is  greater  in  those  grown  in  the 
East,  and  which  are  known  by  the  names  of  Persian 
terries,  Andrinople  herries,  Turkey  and  Morea  herries. 
These  fruits  or  berries  are  small,  of  a  yellowish-green, 
with  two  or  three  united  shells  or  envelopes.  Their 
smell  is  strong  and  nauseous,  and  their  taste  bitter 
and  disagreeable.  They  blacken  by  age,  and  their 
quality  deteriorates.  They  are  gathered  before  com- 
plete ripeness,  and  give  a  fine  yellow  without  fastness. 

Stil-de-grain  is  prepared  by  boiling  for  one  hour,  1 
kilogramme  of  berries  in  8  litres  of  water,  and  pass- 
ing the  decoction  through  a  sieve.  The  berries  re- 
maining upon  the  sieve  are  again  boiled  in  4  litres  of 
water.  This  second  decoction  is  also  passed  through 
the  sieve  and  mixed  with  the  first.  The  liquors  are 
then  filtered,  and  1  kilogramme  of  powdered  alum 
dissolved  in  them.  When  cold,  the  alumina  is  pre- 
cipitated with  carbonate  of  soda,  and  carries  with  it 
the  coloring  matter,  which  will  be  the  darker  as  less 
alum  is  employecj. 

Another  process, — The  berries  are  gathered  before 
maturity,  then  bruised  and  put  into  a  kettle  with  4 
to  5  parts  of  water  and  |  of  alum.     The  yellow 


YELLOW  COLORS. 


367 


liquor  obtained  after  half  an  hour  of  ebullition  is 
filtered  and  mixed  with  J  to  f  of  a  part  of  very  white 
and  fine  chalk,  which  has  been  stirred  in  a  small  quan- 
tity of  water  and  passed  through  a  fine  sieve.  After 
stirring  and  settling,  the  liquor  is  decanted,  and  the 
precipitate  is  washed  and  drained  upon  a  frame. 
When  it  has  acquired  the  proper  consistency  it  is 
divided  into  troches  which  are  dried  at  a  low  tempera- 
ture. 

The  color  which  is  sold  as  stil-de-grain  is  not  al- 
ways prepared  exclusively  with  Avignon  berries ;  it 
is  quite  customary  to  boil  the  berries  with  variable 
quantities  of  weld  (woad),  quercitron  bark,  curcuma, 
yellow  wood,  etc.,  and  to  add  to  the  solution  holding 
alum,  potash,  or  chalk,  until  all  the  coloring  principle 
is  precipitated.    In  such  case  proceed  as  follows : — 

Boil  250  grammes  of  Avignon  berries,  250 
grammes  of  curcuma,  and  180  grammes  of  cartha- 
mus,  in  8  litres  of  water,  and  reduce  to  6  litres ;  re- 
move the  kettle  from  the  fire,  and  add  125  grammes 
of  powdered  sulphate  of  ammonia.  The  liquor  being 
filtered  through  a  cloth,  and  cooled  off  enough  to 
allow  of  the  fingers  being  held  in,  pour  it  slowly 
upon  1.5  kilogrammes  of  powdered  Paris  white, 
which  is  continuously  stirred  with  a  spatula. 

Then  throw  the  mixture  upon  a  cloth  fixed  to  a 
wooden  frame,  and  pour  back  on  top  the  filtering 
liquors  until  they  pass  clear  and  colorless. 

The  Paris  white,  which  has  become  yellow  upon 
the  filter,  is  left  there  until  it  has  acquired  sufficient 
consistency  to  be  divided  into  smaHJumps,  which  are 
allowed  to  dry  thoroughly. 

Stil-de-grain  is  a  fine  yellow  color,  without  fast- 
ness. It  is  employed  for  painting  scenery  in  theatres, 
floors,  etc.  * 


368 


MANUFACTURE  OF  COLORS. 


The  coloring  matter  of  Persian  berries  has  been 
examined  by  Mr.  Kane,  who  has  extracted  by  means 
of  ether  a  yellow  substance  called  chrysorhamnin. 
This  by  boiling  in  water  becomes  oxidized  and  trans- 
formed into  xanthorhamm7i.  Since  then  Mr.  J.  Ortlieb, 
chemist  at  Lille,  has  ascertained  that  the  coloring 
principle  of  Persian  berries  is  held  in  the  state  of 
glucosides,  soluble  in  water.  These  glucosides  may 
be  splitj  either  spontaneously  or  under  the  influence 
of  acids,  into  sugar  and  coloring  substances,  which 
are — 1.  Gold-yellow  granules  of  crystalline  appear- 
ance, produced  in  a  fermenting  decoction,  and  called 
rJiam^nin ;  2.  Another  coloring  matter  afterwards 
spontaneously  deposited,  and  named  hydrate  ofrham- 
niii;  3.  Lastly,  a  product  of  transformation  by  the 
aid  of  sulphuric  acid,  the  hydrate  of  oxyrhamnin. 
There  is  the  same  analogy  between  rhamnin  and  the 
hydrate  of  oxyrhamnin  as  between  the  chrysorhamnin 
and  the  xanthorhamnin  of  Mr.  Kane.  Oxyrhamnin 
is  isomeric  with  euxantic  acid,  the  coloring  principle 
of  Indian  yellow. 

§8.  Weld  lake. 

Weld  or  Woad  (reseda  luteola)  is  a  plant  which 
contains  several  coloring  principles  in  its  leaves, 
stem,  and  seeds.  Mr.  Chevreul  gives  the  name  of 
luteolin  to  one  of  these  principles,  which  is  yellow, 
bright,  and  not  easily  altered  by  the  air  or  dampness. 
It  is  soluble  in  water,  and  becomes  under  the  action 
of  potassa,  soda,  ammonia,  lime,  and  baryta,  of  a 
deep-yellow  color.  Weld  is  used  in  the  preparation 
of  a  lake,  which  is  a  compound  of  luteolin  with 
alumina,  or  of  luteolin  with  lime  and  alumina. 

The  weld  is  cut  into  small  pieces,  which  are  put 


YELLOW  COLORS. 


369 


into  an  enamelled  or  varnished  pot  with  sufficient 
water  to  cover  them.  When  the  water  is  near  the 
boiling  point,  a  weight  of  alum  equal  to  that  of  the 
weld  is  added  and  dissolved.  After  boiling  for  some 
time  the  liquor  is  filtered  and  precipitated  with  a 
solution  of  potash  until  the  latter  begins  to  dissolve 
part  of  the  alumina,  which  is  ascertained  when  the 
effervescence  ceases.  The  whole  is  then  thrown  upon 
a  filter  and  washed  several  times  with  hot  water.  The 
color  is  put  into  the  shape  of  troches. 

We  find  in  an  English  paper  the  following  process 
for  extracting  from  weld  a  pure  yellow  in  impalpable 
powder : — 

Put  about  2  kilogrammes  of  fine  levigated  chalk 
into  a  copper  kettle  with  2  kilogrammes  of  pure 
water.  Boil,  and  stir  with  a  spatula  of  white  wood, 
until  the  chalk  is  thoroughly  tempered.  Add  then 
for  each  kilogramme  of  chalk  from  180  to  200  grammes 
of  powdered  alum.  There  is  an  efiPervescence  pro- 
duced, due  to  the  disengagement  of  carbonic  acid, 
and  the  contents  of  the  kettle  may  run  over  if  the 
addition  of  the  alum  is  not  gradual.  When  no  more 
carbonic  acid  escapes,  the  kettle  is  removed  from  the 
fire. 

Another  kettle  receives  the  weld,  roots  upwards, 
and  enough  water  is  poured  in  to  cover  all  the  parts 
of  the  plant  which  hold  seeds.  A  quarter  of  an 
hour's  boil  is  given,  and  the  plants  are  removed,  roots 
upwards,  to  a  perforated  tub,  where  they  are  allowed 
to  drain.  These  drainings,  mixed  with  the  liquor  of 
the  kettle,  are  filtered  through  a  funnel,  and  contain 
the  coloring  material. 

There  is  no  practical  way  of  ascertaining  exactly  the 
proportion  of  weld  corresponding  to  a  given  weight 
24 


370  MANUFACTURE  OF  COLORS. 

of  chalk,  since  the  quantity  of  seeds  in  a  package  of 
weld  is  variable.  But  should  there  be  too  much 
coloring  matter  prepared,  it  may  be  kept  without 
decomposition,  in  stoneware  or  wooden  vessels,  for 
several  weeks. 

Heat  again  the  kettle  holding  the  aluminous  pre- 
cipitate, and  pour  into  it  the  decoction  of  weld  until 
the  desired  tone  of  color  is  reached.  Then  boil  for  a 
few  minutes,  when  the  operation  is  finished.  In  order 
to  ascertain  that  the  maximum  of  color  is  obtained, 
take  now  and  then  a  small  sample  of  the  mixture, 
and  put  it  upon  a  piece  of  chalk,  where  it  will  dry 
immediately.  If  then  the  pigment  be  spread  with  a 
brush  upon  a  piece  of  white  paper,  it  will  be  easy  to 
judge  of  the  depth  of  the  color.. 

The  contents  of  the  kettle  are  poured  into  a  stone- 
ware or  wooden  vessel,  where  they  are  allowed  to 
settle  for  twenty-four  hours.  The  liquors  being  de- 
canted, the  deposit  is  spread  over  pieces  of  chalk,  and 
dries  rapidly. 

The  decanted  liquors  may  be  employed  for  a  second 
boiling,  adding  the  water  necessary  to  make  up  the 
bulk.  The  plant  itself  may  be  boiled  twice,  and  there 
is  a  certain  saving  of  coloring  matter  by  so  doing. 

We  should  avoid  exposing  this  coloring  substance 
to  the  contact  of  iron,  which  acts  upon  it. 

Manufacturers  of  paper  hangings  consume  the 
greater  proportion  of  weld  lake,  two  kinds  of  which 
are  to  be  found  in  the  trade :  I.  Superfine  lake;  II. 
Lake  'No.  1.  It  is  to  be  regretted  that  this  color 
is  not  fasf,  and  on  this  account  it  is  rarely  employed 
for  oil  or  water  colors. 

MM.  P.  Schutzenberger  and  A.  Paraf  have  recently 


YELLOW  COLORS. 


371 


made  the  analysis  of  luteolin,  the  coloring  principle 
of  weld,  and  have  found  its  composition  to  be — 

Carbon   62.068 

Hydrogen  ....  3.448 
Oxygen   34.484 

100.000 

The  chemical  formula  of  luteolin,  dried  at  150°  C, 
is,  therefore,  C^^WO^^ ;  that  of  crystallized  luteolin 
is  C'WO'MIO. 

By  treating,  at  200°  C,  luteolin  with  anhydrous 
phosphoric  acid,  we  obtain  a  red  substance  which 
with  ammonia  makes  a  violet  solution. 

When  luteolin  is  heated  in  sealed  tubes  with 
caustic  ammonia,  for  three  or  four  days,  and  at  the 
temperature  of  100°  C,  it  becomes  entirely  dissolved, 
and  the  solution  is  of  a  deep-yellow.  This  liquor, 
being  evaporated  to  dryness,  leaves  a  dark  residue 
called  luteolamide,  which  does  not  disengage  am- 
monia by  a  treatment  with  caustic  lime.  On  the  other 
hand,  it  produces  ammonia  with  caustic  potassa. 

§  9.  Lakes  of  quercitron  and  yellow  wood. 

Quercitron,  such  as  is  found  in  the  trade,  is  a  fawn- 
colored  powder  mixed  with  fibrous  portions,  ground 
from  the  bark  of  an  American  oak  (^quercus  nigra). 
This  bark  contains  a  yellgw  principle  called  querci- 
trin,  which,  viewed  with  a  magnifying  glass,  appears 
of  a  light  and  slightly  grayish-yellow.  Alum-water 
changes  it  to  a  fine  yellow.  By  processes  similar  to 
those  employed  with  weld,  it  is  possible  to  obtain 
from  quercitron  a  lake,  which  is  not,  however,  so 
handsome  as  that  made  from  weld. 

Yellow  wood  (Morus  tinctoria)  contains  a  coloring 


372 


MANUFACTURE  OF  COLORS. 


principle  called,  by  Mr.  Chevreul,  morin.  Alum, 
with  a  decoction  of  yellow  wood,  furnishes  a  canary- 
yellow  precipitate.  This  wood  may,  therefore,  be 
employed  for  the  preparation  of  a  yellow  lake,  which, 
however,  in  beauty  and  durability,  is  inferior  to  that 
of  weld. 

We  shall  examine,  further  on,  new  processes  for  the 
manufacture  of  vegetable  lakes  of  a  red  color,  and 
which  may  be  applied  to  the  preparation  of  yellow 
ones. 

§  10.  Chrome  yellows. 

Chemistry  and  the  arts  are  indebted  to  Yauquelin 
for  the  discovery  of  chromium,  a  peculiar  metal  which 
he  found,  in  1797,  in  a  sample  of  Siberian  red  lead 
(chromate  of  lead).  "Vauquelin  distinguished  in  the 
new  metal  the  remarkable  coloring  power  of  its  com- 
binations ;  indeed,  the  name  which  he  chose  means 
color.  Among  the  combinations  of  chromium  those 
most  employed  in  the  arts  are  the  chromates  of  lead, 
lime,  and  baryta.  The  neutral  chromate  of  lead  is  of 
a  very  fine  and  bright  yellow,  which  is  used  for 
printing  on  cloths  and  on  porcelain,  for  paper  hangings, 
and  for  house  and  carriage  painting.  All  the  other 
chromates  have  different  colors,  and  Thenard  believes 
that  several  of  them  will  be  employed  for  various 
colors  and  hues  which  cannot  be  obtained  from  other 
substances. 

Since  all  the  other  chromates  are  prepared  with 
chromate  of  potassa,  we  think  it  desirable  that  we 
should  endeavor  to  cause  its  preparation  to  become 
well  known. 

One  of  the  processes  for  the  manufacture  of  this 
salt  consists  in  calcining  at  a  high  temperature  a 
mixture  of  nitrate  of  potassa  and  chrome  ore,  the 


YELLOW  COLORS. 


373 


latter  being  a  compound  of  the  oxides  of  chromium 
and  iron,  with  some  silica,  alumina,  and  magnesia. 
The  proportion  of  nitre  is  one-half,  or,  at  most,  two- 
thirds  of  the  weight  of  the  chrome  ore  when  it  is  very 
hard.  Should  too  great  an  excess  of  nitre  be  present, 
the  earthy  substances  would  be  corroded  by  the  alkali 
of  the  nitrate,  and  the  chromate  be  rendered  impure. 
The  oxygen,  disengaged  from  the  nitre  by  heat, 
oxidizes  the  iron  and  acidifies  the  chromium.  The 
chromate  of  potassa  is  freely  soluble  in  water,  and  is 
separated  by  washing  the  calcined  residuum.  The 
insoluble  portions  still  contain  a  certain  proportion 
of  undecomposed  chrome  ore. 

Chromate  of  potassa  is  of  a  fine  lemon-yellow  color, 
crystallizes  in  prisms,  and  is  composed  of — 

Chromic  acid  100 

Potassa   92.307 

It  is  also  known  under  the  names  of  neutral  chro- 
mate  and  yellow  chromate  of 'potash.  There  is  another 
well-known  salt,  the  bichromate  of  potassa,  or  acid 
chromate,  which  is  of  a  handsome  red  color,  and 
crystallizes  in  quadrangular  prisms.  It  is  less  soluble 
in  water  than  the  neutral  chromate,  and  contains 
twice  as  much  coloring  substance  (chromic  acid). 
Its  composition  is — 

Chromic  acid  100 

Potassa  46.153 

1.  Neutral  Chromate  of  Lead. 

A  neutral  chromate  of  lead,  of  a  very  rich  tone, 
will  be  obtained  by  dissolving,  for  instance,  10  kilo- 
grammes of  neutral  chromate  of  potassa  in  100  litres 
of  hot  water.  We  also  dissolve  in  another  vessel,  20 
kilogrammes  of  neutral  acetate  of  lead  (sugar  of  lead) 
in  50  litres  of  water.    When  the  solution  of  chromate 


374 


MANUFACTURE  OF  COLORS. 


of  potassa  is  boiling,  we  carefully  pour  into  it  that  of 
acetate  of  lead,  and  allow  the  precipitate  to  settle. 
This  latter  is  washed  several  times  by  decantation, 
drained  upon  cloth  filters,  and  dried  in  a  stove-room. 
There  should  remain  a  small  excess  of  chromate  of 
potassa  in  the  liquor,  in  order  to  prevent  the  forma- 
tion of  a  basic  chromate  of  lead,  which  will  impair  the 
light  yellow  of  the  neutral  chromate. 

If  we  substitute  nitrate  of  lead  for  the  acetate,  the 
product  will  be  still  brighter.  The  proportions  will 
then  be,  forty-two  parts  of  nitrate  of  lead,  and  nine- 
teen parts  of  bichromate  of  potassa.  The  comxDosition 
of  the  neutral  yellow  chromate  of  lead  is — 

Chromic  acid  31. U 

Oxide  of  lead   .  68.29 

100.00 

Baron  Liebig  has  indicated  another  process  for  the 
manufacture  of  a  very  dense  neutral  chromate  of 
lead : — 

The  sulphate  of  lead,  left  as  a  cheap  secondary  pro- 
duct in  dye  works,  is  digested  and  stirred  in  a  warm 
solution  of  neutral  chromate  of  potassa.  A  double 
decomposition  takes  place,  by  which  a  soluble  sulphate 
of  potassa  and  an  insoluble  chromate  of  lead  are 
formed.  The  liquors  are  decanted,  and  the  precipi- 
tate is  washed,  drained,  divided  into  square  prisms, 
and  dried  in  a  stove-room  at  the  temperature  of  50°  C. 

This  chromate  is  cheaper,  and  quite  as  fine  as  the 
preceding  one,  although  it  is  more  dense  and  does 
not  cover  so  well.  It  generally  contains  a  certain 
proportion  of  imdecomposed  sulphate  of  lead. 

Neutral  chromate  of  lead  possesses  great  body, 
and  a  fine  yellow  color,  the  tones  of  which  vary  con- 


YELLOW  COLORS. 


375 


siderably  with  different  manufacturers.  It  can  be 
had  from  a  light  yellow  to  an  orange-red,  and  these 
differences  are  due  to  the  mode  of  preparation. 

2.  Basic  Chromate  of  Lead. 

This  yellow,  known  in  the  trade  under  the  names 
of  gold  yellow  or  orange  paste,  possesses  a  reddish- 
yellow  hue,  which  is  quite  pleasing.  It  is  a  combina- 
tion of  chromic  acid  with  more  oxide  of  lead  than 
is  contained  in  the  neutral  chromate. 

The  most  economical  process  for  preparing  this 
basic  chromate  or  chrome  yellow  consists  in  boiling, 
for  one  hour  at  most,  fifteen  parts  of  chromate  of  lead 
with  two  parts  of  caustic  lime  fused  in  a  small  pro- 
portion of  water.  By  the  reaction  which  takes  place, 
a  soluble  chromate  of  lime  is  formed,  and  the  remain- 
ing basic  chromate  of  lead  is  washed,  drained,  dried, 
and  heated  in  a  crucible  until  the  desired  hue  is 
obtained. 

We  may  also  treat  three  parts  of  neutral  chromate 
of  lead  by  two  parts  of  oxide  of  lead.  Or,  a  solution 
of  acetate  of  lead  may  be  poured  into  another  boiling 
solution  of  chromate  of  potassa,  holding  an  excess  of 
caustic  potassa  or  soda.  The  precipitate  resembles 
vermilion. 

A  basic  chromate  of  lead  is  prepared  by  boiling, 
for  several  hours,  equal  weights  of  white  lead  and 
chromate  of  potassa.  There  is  formed  a  soluble 
carbonate  of  potassa,  and  a  basic  chromate  of  lead, 
which  is  heated  in  a  crucible  until  it  acquires  a  scarlet 
color. 

Lastly,  if  we  melt  in  a  crucible  nitrate  of  potassa, 
and  add  dry  and  powdered  chromate  of  lead  by  small 
quantities  at  a  time,  there  is  a  production  of  red 


376 


MANUFACTURE  OF  COLORS. 


nitrous  fumes,  of  chromate  of  potassa,  and  of  basic 
chromate  of  lead,  which  latter  sinks  to  the  bottom. 
The  chromate  of  potassa  is  poured  out  while  it  is  still 
hotj  and  the  crucible  is  left  to  cool  off.  The  chromate 
of  lead  is  removed,  washed  several  times,  drained, 
and  dried  in  a  stove-room.    Its  color  is  cinnabar  red. 

The  trade  furnishes  a  quantity  of  basic  chromates 
of  lead,  with  hues  varying  from  a  reddish-yellow  to  a 
vermilion-red. 

Mr.  Merimee  asserts  that  alumina,  added  to  inferior 
qualities  of  chromates,  preserves  their  brightness. 

It  is  probable  that  the  variations  in  hue  and  tone 
are  often  due  to  small  proportions  of  sulphate  of  lead, 
and  of  chromates  of  lime,  baryta,  and  alumina,  almost 
always  found  in  chromates  of  lead. 

3.  Jonquil  Chrome  Yellow  of  Winterfeld, 

The  jonquil  chrome  yellow  of  Mr.  "Winterfeld  is  a 
basic  chromate  of  lead  which  is  not  calcined.  There- 
fore, the  oxide  of  lead  is  hydrated.  It  is  prepared  as 
follows : — 

Dissolve  33  parts  of  acetate  of  lead  in  100  parts  of 
pure  water,  and  filter.  The  clear  liquor  is  kept  in  a 
vessel  of  sufficient  capacity  to  hold  about  twice  that 
volume  of  liquid. 

In  another  vessel  dissolve  22  parts  of  crystallized 
carbonate  of  soda  in  60  parts  of  pure  water,  and  filter. 

The  soda  solution  is  then  slowly  poured,  stirring 
all  the  while,  into  that  of  acetate  of  lead,  and  there 
results  a  white  precipitate  which  is  allowed  to  settle. 
The  supernatant  liquor  is  a  solution  of  acetate  of 
soda. 

During  these  operations,  another  solution  has  been 
prepared  with  17.15  parts  of  neutral  chromate  of 


YELLOW  COLORS. 


377 


potassa  in  50  parts  of  water.  It  is  poured  upon  the 
precipitate  of  carbonate  of  lead,  and  the  stirring  is 
continued  until  all  of  the  chromate  of  potassa  is 
decomposed,  that  is,  until  the  clear  liquor  is  no  longer 
colored  yellow. 

The  chrome  yellow  thus  obtained  is  washed  with 
pure  water,  drained  upon  a  filter,  pressed,  and  then 
cut  into  blocks  and  dried.  The  product  is  27  parts 
of  chrome  yellow,  from  the  proportions  indicated 
above. 

The  jonquil  chrome  yellow  of  Winterfeld  is  the 
lighter  in  color,  as  the  proportion  of  acetate  of  lead 
is  greater. 

4.  Cologne  Yellow. 

This  yellow  is  obtained  by  decomposing  sulphate 
of  lime  and  chromate  of  lead  with  a  solution  of  soda. 

Another  way  is  to  have  very  finely  powdered 
sulphate  of  lime  kept  fioating  in  a  solution  of  chro- 
mate of  potassa,  and  to  precipitate  with  neutral  ace- 
tate of  lead. 

This  color  is  very  bright  and  fast,  and  is  used  for 
distemper  painting.  It  is  a  compound  of  chrome 
yellow  with  the  sulphates  of  lime  and  lead. 

Troches  of  this  yellow,  analyzed  by  Mr.  Boutron- 
Chartard,  had  the  following  composition : — 

Sulphate  of  lime  60 

Sulphate  of  lead  15 

Chromate  of  lead  25 

100 

Chrome  yellows  are  in  great  demand  for  oil  paint- 
ing, on  account  of  their  brightness  and  durability. 
Moreover,  mixed  with  vermilion,  they  give  chamois 
hues with  white  lead,  straw  yellow  and  jonquil  ] 


378 


MANUFACTURE  OF  COLORS. 


with  Prussian  blue,  magnificent  greens,  which  are 
not,  however,  lasting. 

Since  these  pigments  possess  great  intensity  or 
coloring  power,  they  are  often  adulterated  with  sul- 
phate of  lime,  chalk,  white  lead,  sulphate  of  lead, 
starch,  etc.  Several  of  these  substances,  however, 
cannot  be  considered  as  fraudulent  mixtures  because 
they  result  from  the  mode  of  preparation  itself,  or 
have  been  added  to  arrive  at  a  desired  tone  of  color, 
l^evertheless,  as  the  manipulations  necessary  for 
ascertaining  the  foreign  substances  are  quite  com- 
plicated, we  advise  the  consumer  not  to  make  the 
analysis  himself,  but  to  entrust  it  to  the  hands  of  an 
experienced  chemist. 

5.  Chr ornate  of  Lime. 

If  we  pour  chromate  of  potassa  into  a  solution  of 
chloride  of  calcium,  nitrate  of  lime,  or  other  soluble 
lime  salt,  we  obtain  a  precipitate  of  chromate  of  lime, 
which  is  of  a  fine  straw-yellow  color,  and  is  used  in 
distemper  painting.  Its  covering  power  is  small,  but 
it  does  not  blacken  like  the  chromates  of  lead. 

In  the  manufacture  of  chromate  of  lime  the  solu- 
tions employed  are — one  of  bichromate  of  potassa 
saturated  with  carbonate  of  soda,  and  one  of  chloride 
of  calcium  obtained  by  dissolving  chalk  in  hydro- 
chloric acid.  The  latter  solution  is  slowly  poured 
into  the  former,  and  the  precipitate  of  chromate  of 
lime  is  allowed  to  settle  and  is  then  drained,  washed, 
and  dried. 

6.  Cht'omate  of  Baryta. 

A  solution  of  bichromate  of  potassa  is  saturated 
with  carbonate  of  soda,  and,  after  evaporation  and 
cooling,  a  double  chromate  of  potassa  and  soda  is 


YELLOW  COLORS. 


379 


obtained.  On  the  other  hand,  carbonate  of  baryta  is 
dissolved  in  hydrochloric  acid,  and  the  chloride  of 
barium  is  made  to  crystallize.  Two  separate  solu- 
tions are  effected,  one  with  25  parts  of  the  double 
chromate,  and  the  other  with  20  parts  of  chloride  of 
barium ;  these  are  mixed  cold,  or  better  still,  hot,  and 
are  kept  well  stirred.  The  precipitate  is  a  fine  lemon- 
yellow  chromate  of  baryta. 

This  pigment  is  employed  in  the  manufacture  of 
paper  hangings,  and  for  adulterating  chrome-yellows. 
It  is  open  to  the  objection  of  darkening  in  the  air, 
and  is  sometimes  improperly  called  ultramarine  yellow. 
We  shall  again  examine  the  chromate  of  baryta  fur- 
ther on. 

"We  now  introduce  an  extract  from  a  memoir  pub- 
lished by  Mr.  Habich  in  the  Technologiste^  vol.  xviii. 
page  171,  upon  the  manufacture  of  the  neutral  chrome 
yellow,  the  red  or  basic  chromate,  and  the  chrome 
green. 

A.  Chrome  Yellow. 

The  manufacturers  of  chrome  yellow,  who  distin- 
guish themselves  by  the  beauty  of  their  products  and 
by  their  skill  in  obtaining  a  given  hue,  says  Mr. 
Habich,  employ  soluble  lead  salts.  It  is  true  that 
the  sulphate  of  lead,  obtained  in  large  quantities  in 
dye  works,  gives  a  cheaper  chrome  yellow ;  but  its 
hue  is  not  constantly  the  same,  and  it  is  far  inferior 
in  depth  and  brightness  of  color  to  other  chrome 
yellows  prepared  by  other  processes.  On  the  other 
hand,  it  appears  to  suit  very  well  for  certain  green 
colors  obtained  by  mixture,  such  as  the  green  cinna- 
bar, the  chrome  green,  etc. 

We  have  first  to  explain  how  to  prepare  a  solution 
of  lead. 


380 


MANUFACTURE  OF  COLORS. 


Small  wooden  tubs,  45  to  50  centimetres  high  and 
1  metre  in  diameter,  are  disposed  one  on  top  of  the 
other,  so  that  their  contents  may  pass  through  a 
spigot  at  the  bottom  into  the  lower  ones.  Four  such 
tubs  are  sufficient  for  the  apparatus. 

These  tubs  are  filled  with  thin  ribbons  of  lead 
prepared  as  follows:  The  molten  lead  is  slowly 
poured,  by  means  of  an  iron  ladle,  into  water  which  is 
kept  stirred  with  a  broom.  Practice  will  soon  teach 
how  to  arrive  at  the  greatest  thinness  of  metal,  the 
main  points  being  to  ascertain  the  proper  height  of 
the  ladle  above  the  surface  of  the  water  and  the 
thickness  of  the  stream  of  molten  lead. 

When  all  the  tubs  are  charged  with  lead  the  spig- 
ots are  closed,  and  the  upper  tub  is  filled  with  strong 
alcohol  vinegar,  which  should  be,  as  far  as  practicable, 
free  from  the  coloring  and  extractive  matters,  gum, 
sugar,  etc.  After  a  few  minutes  the  spigot  is 
opened  in  order  to  allow  the  liquor  to  run  into  the 
second  tub,  and  afterwards  into  the  third  and  the 
fourth.  This  first  passage  of  the  vinegar  through 
these  tubs  dissolves  but  a  slight  proportion  of  lead. 
Indeed,  this  first  operation  simply  consists  in 
thoroughly  wetting  the  metal,  and  aiding  its  further 
oxidation,  which  is  seen  to  progress  favorably  when 
the  lead  becomes  covered  with  a  bluish-white  pellicle. 
For  dissolving  the  oxide  of  lead  formed  the  first  tub 
is  again  filled  with  vinegar.  After  half  an  hour  the 
liquor  of  the  first  tub  is  emptied  into  the  second,  and 
so  on  until  the  solution  is  saturated  with  lead.  It  is 
then  collected  in  a  larger  tub  below.  When  the 
oxidation  of  the  lead  goes  on  rapidly,  the  saturated 
liquor  contains  a  basic  acetate  of  lead,  which,  by 
exposure  to  the  carbonic  acid  of  the  air,  is  soon 


YELLOW  COLORS. 


381 


covered  with  a  white  film  of  carbonate  of  lead.  For 
the  manufacture  of  chrome  yellow  enough  acetic  acid 
is  added  to  this  solution  for  slightly  reddening  blue 
litmus  paper.  The  liquor  is  then  put  into  large 
settling  tanks  for  the  deposition  of  the  impurities, 
and  there  should  always  be  a  good  supply  of  it  at  hand. 

Another  tank  also  contains  a  stock  of  a  solution  of 
bichromate  of  potassa  prepared  as  follows :  25  kilo- 
grammes of  this  salt  are  dissolved  in  ten  times  their 
weight  of  hot  water,  in  a  copper  kettle,  and  then 
poured  into  the  tank  with  enough  water  to  make 
about  5  hectolitres.  Altogether  20  parts  of  water  to 
1  of  bichromate  of  potassa. 

In  order  to  operate  rapidly  and  with  certainty,  the 
following  articles  are  needed :  1,  a  tub  of  white 
pine,  1.25  metres  high,  and  of  equal  diameter,  with 
several  holes  at  different  heights,  and  closed  with 
plugs ;  2,  a  small  wooden  tub,  holding  about  2  hecto- 
litres, and  provided  with  a  spigot  near  the  bottom  ; 
3,  two  pails,  holding  each  from  10  to  12  litres ;  4,  a 
graduated  tube ;  5,  a  barrel  covered  with  a  filter ;  6, 
a  wooden  platform  or  tray  edged  all  round. 

Before  beginning  the  operation  it  is  necessary  to 
ascertain  the  degree  of  concentration  of  the  lead 
liquor,  which  dejDends  on  the  very  variable  strength 
of  the  vinegar  employed.  Experimental  tests  are 
therefore  applied,  in  order  to  ascertain  how  many 
volumes  of  the  solution  of  lead  are  necessary  to 
saturate  ten  volumes  of  the  chromic  solution,  that  is, 
to  obtain  after  precipitation  a  liquor  holding  neither 
oxide  of  lead  nor  chromic  acid. 

Ten  volumes  of  the  solution  of  bichromate  of 
potassa  are  measured  in  the  graduated  tube,  and  then 
poured  into  a  tumbler,  which  also  receives  the  water 


382 


MANUFACTURE  OF  COLORS. 


with  which  the  tube  is  rinsed.  The  same  tube  is  now 
filled  with  the  lead  solution,  and  the  volume  noted. 
It  remains  now  to  let  the  lead  liquor  fall  into  that  of 
bichromate,  drop  by  drop,  as  long  as  a  precipitate 
takes  place.  The  volume  of  lead  solution  poured  out 
is  marked  down,  and  indicates  the  number  of  volumes 
of  the  stock  of  lead  solution  necessary  to  precipitate 
ten  volumes  of  the  liquor  of  bichromate. 

For  obtaining  the  various  hues  of  chrome  yellow 
there  are  several  methods,  which  are  based  upon  the 
chemical  composition  of  the  different  yellows  obtained 
from  chromium.  These  compositions  should  there- 
fore be  carefully  studied  if  we  desire  to  operate  with 
certainty. 

When  we  precipitate  a  solution  of  lead  by  one  of 
red  bichromate  (acid)  or  of  yellow  chromate  (neutral) 
of  potassa,  the  dark  lemon-yellow  precipitate  is,  in 
either  case,  a  neutral  chromate  of  lead,  which  has  the 
same  composition,  that  is,  112  parts  of  oxide  of  lead 
to  52  parts  of  chromic  acid. 

There  is  another  combination  called  chrome  red, 
and  we  shall  see  its  preparation  further  on.  It  con- 
tains but  one-half  of  the  chromic  acid  of  the  neutral 
chromate,  that  is,  26  parts  of  acid  to  112  parts  of  oxide 
of  lead.  If  the  chromic  solution  holds  a  certain  quan- 
tity of  free  alkali,  the  latter  separates  from  the  lead 
solution  a  proportional  amount  of  oxide  of  lead, 
which,  mixing  with  chromate  of  lead,  colors  it  red. 
If,  therefore,  we  are  enabled  to  prepare  the  mixtures 
with  accuracy,  it  will  be  possible  to  produce  all  the 
desired  tones  and  hues  ranging  from  dark  lemon- 
yellow  to  chrome-red.  The  process  consists  in  adding 
a  caustic  lye  of  known  strength  to  the  washed  pre- 
cipitate of  neutral  chromate. 


YELLOW  COLORS. 


383 


There  are  two  double  combinations  of  neutral  chro- 
mate  with  sulphate  of  lead  (Cologne-yellow)  corres- 
ponding with  the  formulae  PbO.CrO'  +  PbO.SO'  and 
PbO.CrO'+2PbO.SOl  The  first  takes  place  when  a 
corresponding  proportion  of  sulphuric  acid  is  added  to 
the  chromic  solution  employed  for  precipitating  the 
lead  liquor.  A  solution,  prepared  as  we  have  previously 
said,  holds  2.6  kilogrammes  of  chromic  acid  per  hecto- 
litre, and  requires  1.82  kilogramme  of  concentrated 
sulphuric  acid.  The  precipitate,  formed  and  collected 
upon  a  filter,  increases  in  volume  considerably.  After 
drying,  it  is  a  very  light  pigment  of  a  light  lemon- 
yellow  color,  which  is  remarkably  fine. 

The  second  combination  takes  place  when  the  pro- 
portion of  sulphuric  acid  is  3.65  kilogrammes  per 
hectolitre  of  chromic  solution.  It  does  not  increase 
in  volume  as  does  the  former  article,  but,  after  drying, 
the  pigment  is  of  a  sulphur  color,  with  a  smooth 
fracture. 

The  first  combination  is  employed  especially  for 
preparing  ordinary  chrome  yellows,  mixed  with  the 
sulphates  of  baryta,  lime,  etc.,  and  is  remarkable  for 
its  covering  power.  The  second  combination  is  par- 
ticularly suitable  for  the  bright  greens  resulting  from 
the  mixture  of  Prussian  blue  with  chrome  yellow. 

Since  the  tones  of  color  of  these  two  combinations 
are  so  diflPerent,  it  is  evident  that  by  varying  the  pro- 
portion of  sulphuric  acid,  it  will  be  possible  to  obtain 
all  the  intermediate  tones  between  light  lemon  yellow 
and  sulphur  yellow. 

The  success  in  the  preparation  of  certain  chrome 
yellows  often  depends  upon  the  mode  of  working, 
which  I  shall  now  indicate. 

For  preparing  the  combination  PbO.CrO^  +  PbO. 


384 


MANUFACTURE  OF  COLORS. 


SO^,  a  tub  is  filled  to  two-thirds  of  its  capacity  with 
water,  and  then  with  the  quantity  of  lead  liquor  neces- 
sary for  decomposing  125  litres  of  chromic  solution 
holding  6.25  kilogrammes  of  bichromate  of  potassa. 
This  quantity  of  chromic  solution  is  held  in  the  small 
tub,  and  is  mixed  with  3.25  kilogrammes  of  sulphuric 
acid.  This  mixture  is  then  allowed  to  run  slowly  into 
the  lead  solution,  which  is  kept  constantly  stirred. 
After  settling,  the  supernatant  liquor,  rich  in  acetic 
acid,  is  decanted,  and  the  deposit  is  twice  washed  with 
water  in  the  tub,  before  it  is  collected  and  drained  upon 
a  cloth.  As  soon  as  drained,  the  pulp  is  spread  upon  a 
wooden  tray.  These  operations  of  washing  and  drain- 
ing should  be  effected  as  rapidly  as  possible,  in  order 
that  the  pulp  shall  not  swell  on  the  cloth,  but  on  the 
ti'ay.  Indeed,  should  the  swelling  take  place  upon 
the  cloth,  the  pulp  would  become  denser  when  spread 
upon  the  tray,  and  would  thus  lose  a  portion  of  that 
lightness  which  is  so  much  sought  for  in  it.  When 
everything  goes  on  without  loss  of  time,  the  pulp  is 
spread  upon  the  trays,  which  are  deposited  in  a  cool 
place  as  long  as  the  swelling  continues,  and  until  the 
paste  has  acquired  consistency.  The  mass  is  then 
cut  into  large  cubes,  which  are  dried  in  the  sun. 
Their  crust  is  generally  disfigured  by  the  crystalliza- 
tion of  a  certain  proportion  of  undecomposed  chromate 
of  potassa,  which  cannot  be  removed  by  the  most 
thorough  washing.  This  is  made  to  disappear  by 
means  of  a  brush,  taking  care  not  to  inhale  the  flying 
dust.  The  sweepings  are  kept  for  an  inferior  quality 
of  yellow,  or  for  the  preparation  of  green  cinnabar 
(chrome  green). 

The  second  sulphur  yellow  combination  is  obtained 
in  the  same  manner,  only  that  the  proportion  of  sul- 


YELLOW  COLORS. 


385 


phiiric  acid  is  double,  that  is,  6.5  kilogrammes  per 
125  litres  of  chromic  liquor.  The  precipitate  is  rap- 
idly washed,  filtered,  drained,  and  pressed.  The  cut 
blocks  are  dried  in  the  shade  in  a  well-ventilated 
room.  If  all  these  operations  are  not  effected  rapidly, 
it  may  happen  that  a  slight  admixture  of  the  first  com- 
bination will  cause  the  pigment  to  swell  up,  and  thus 
destroy  the  smooth  and  even  fracture  required  by  the 
trade. 

B.  Chrome  Red  or  Basic  Chromate. 

Chrome  red  is  another  color,  the  preparation  of 
which  is  nearly  related  to  that  of  chrome  yellow. 

All  the  chrome  reds,  from  the  darkest  cinnabar  red 
to  a  minium  red  without  lustre,  are  simply  distin- 
guished by  the  size  of  the  crystals  of  their  powder, 
and  the  observation  may  easily  be  made  with  a  micro- 
scope. If  various  chrome  reds  of  the  same  hue,  but 
with  different  intensities  of  color,  are  reduced  by 
grinding  to  the  same  degree  of  comminution,  their 
powder  wall  then  possess  the  same  intensity  of  color- 
ation, but  the  brightness  disappears. 

Therefore,  if  chrome  reds  are  desired  very  bright 
and  intense  in  color,  we  should  search  for  the  condi- 
tions which  aid  in  the  formation  of  the  crystals.  One 
of  the  best  processes  consists  in  avoiding  all  agita- 
tion, which  may  prevent  the  formation  of  crystals  or 
destroy  them. 

I  recommend  in  that  respect,  the  following  method: 
Chrome  yellow  is  precipitated  in  the  usual  manner, 
without  sulphuric  acid,  and  is  washed  carefully. 
After  draining,  the  mass  is  well  stirred,  and  six  or 
eight  equal  samples  are  taken  from  it  and  put  into 
glass  vessels  of  the  same  size  and  thickness  of 
25 


386 


MANUFACTUKE  OF  COLORS. 


material.  Each  sample  receives  a  diflPerent  volume  of 
a  caustic  lye  of  potassa  or  soda,  marking  about  20° 
Be.  For  instance,  to  5  volumes  of  paste  we  add  2, 
2J,  3,  3|,  4,  5,  etc.  volumes  of  lye.  The  different  mix- 
tures are  thoroughly  and  rapidly  stirred,  but  the 
chemical  reaction  is  allowed  to  take  place  without 
any  disturbance.  After  examination  of  the  quality 
of  the  products,  the  relative  proportions  of  pulp  and 
lye^  are  noted  down  for  the  best  hues  of  color.  If 
there  be  a  stock  of  lye  of  known  strength,  this  experi- 
ment is  sufficient  to  reproduce  on  a  large  scale  the 
desired  color. 

The  operation  is  then  performed  in  a  large  tub, 
which  receives  the  mixture  of  pulp  and  caustic  lye  in 
the  proportions  previously  found.  The  changes  in 
the  color  are  soon  perceived,  and  the  reaction  requires 
about  twelve  hours.  After  that  length  of  time,  the 
lye  which  has  appropriated  a  great  deal  of  chromic 
acid  is  decanted.  The  pigment  is  carefully  washed 
with  pure  water  once  in  the  tub,  and  the  mass  is 
gently  stirred.  The  washing  is  continued  upon  the 
filters,  by  throwing  water  upon  the  pulp,  and  in  this 
manner  there  is  less  friction  between  the  crystals 
which  retain  their  deep  color. 

It  is  well  understood  that  a  very  dark  chrome  red, 
which  is  highly  crystalline,  is  not  expected  to  possess 
great  covering  power. 

C.  Gi^eens  by  Mixtures  {Cinnahar  Green^  Chrome  Green). 

This  branch  of  the  manufacture  of  colors  presents 
but  few  interesting  facts. 

*  Too  considerable  a  proportion  of  caustic  lye  will  fail  to  deepen 
the  red  color.  Indeed,  chrome  red  is  entirely  soluble  in  an  excess 
of  lye,  and  forms  needle-like  crystals,  holding  potassa,  when  the 
caustic  solution  has  absorbed  carbonic  acid  from  the  air. 


YELLOW  COLORS. 


387 


Many  manufacturers  have  tried,  without  success, 
to  prepare  a  fine  chrome  green  having  a  smooth 
fracture,  by  mixing  Paris  blue  with  pure  chrome 
3^ellow.  A  good  product  will  be  obtained  if  a  light 
chrome  yellow  with  smooth  fracture  be  employed,  and 
if  the  mixture  be  compressed  immediately  after  the 
addition  of  the  blue. 

A  chrome  green,  with  smooth  fracture,  may  be 
prepared  by  an  admixture  of  recently  precipitated 
hydrate  of  alumina.  A  solution  of  12  kilogrammes 
of  alum  (free  from  iron)  in  hot  water,  is  decomposed 
by  a  clear  lye  of  soda.  The  precipitate  is  washed  and 
mixed  with  about  5  kilogrammes  of  finely  ground 
sulphate  of  lime,  7  hectolitres  of  the  above  indicated 
chrome  solution,  and  the  required  proportion  of  Prus- 
sian blue.    The  lead  solution  is  then  added. 

For  the  manufacture  of  green  cinnabar  it  is  important 
to  add  a  small  proportion  of  indigo  carmine,  which 
gives  great  brightness  and  a  bluish  tinge.  This  is  the 
best  method  for  preparing  that  bright  pigment  called 
silky  green  or  seiden  griin ;  and  in  the  manufacture 
of  fancy  papers,  it  has  been  customary  for  a  long  time, 
to  increase  the  brightness  of  the  coats  of  green  cin- 
nabar with  a  final  coat  of  a  solution  of  indigo  carmine. 

§  11.  Various  chromates. 

Chromate  of  zinc  was  first  proposed  as  a  yellow 
pigment  by  MM.  Leclaire  and  Barruel.  They  gave 
it  the  name  of  hutter  cup  (houton  d^or)  yellow^  and 
thus  describe  its  preparation  in  the  patent  they  have 
conjointly  taken  out : — 


388 


MANUFACTURE  OF  COLORS. 


1.  Chr ornate  of  Zinc. 

"  The  chromate  of  zinc  is  a  salt  of  which  little  is 
known.  Very  few  authors  mention  it,  and  they  do 
not  agree  as  to  its  physical  properties. 

"From  our  researches,  trials,  and  experiments,  we 
have  determined  upon  the  following  processes  for  pre- 
paring this  salt : — 

"  1.  The  employment  of  a  double  salt  of  potassa 
and  soda,  that  is,  a  double  chromate  of  potassa  and 
soda. 

''2.  The  employment  of  a  sulphate  of  zinc  pre- 
viously deprived  of  iron  or  copper  salts,  and  made 
sufficiently  neutral  by  ammonia,  or  better  still,  by 
carbonate  of  soda. 

"  3.  The  neutralization  of  the  mother  liquors  and 
of  the  first  washings  of  the  chromate  of  zinc,  by  the 
carbonate  of  soda.  This  operation  is  necessary  for 
finishing  the  preparation  of  the  chromate. 

"  4.  Utilizing  the  washings  of  the  chromate  of  zinc 
for  the  production  of  a  green  which  is  fast  and  un- 
alterable, by  making  sulphuretted  hydrogen  or  sulphur 
act  upon  these  hot  mother  liquors. 

"  We  make  upon  a  sand  bath,  and  in  stoneware 
vessels,  a  peculiar  solution  of  a  neutral  chromate  of 
soda  and  potassa. 

"  We  should  observe  that  this  neutral  chromate  of 
soda  and  potassa  is  chosen  on  account  of  the  economy 
in  its  manufacture.  Indeed,  the  neutral  chromate  of 
potassa  is  more  expensive  than  our  double  chromate, 
or  than  the  bichromate  of  potassa,  with  which  we 
prepare  our  double  chromate  by  the  following 
formula : — 

"  We  take  100  kilogrammes  of  bichromate  of  po- 


YELLOW  COLORS. 


389 


tassa,  which  we  powder  and  dissolve  in  hot  water. 
We  then  add,  by  portions  at  a  time,  95  kilogrammes 
of  crystallized  carbonate  of  soda,  which  is  the  equiva- 
lent proportion  for  obtaining  a  neutral  double  chro- 
mate  of  potassa  and  soda.  The  commercial  sulphate 
of  zinc  is  dissolved  in  three  times  its  weight  of  water, 
in  stoneware  jars  placed  upon  a  sand  bath.  A  stream 
of  chlorine  is  then  passed  through  the  hot  solution, 
and  peroxidizes  the  iron  salt  present.  There  is  also 
sometimes  a  certain  proportion  of  sulphate  of  copper. 
When  the  solution  has  become  turbid  from  a  yellow 
and  flaky  precipitate  of  subsulphate  of  sesquioxide  of 
iron,  the  stream  of  chlorine  is  interrupted,  and  a  slight 
excess  of  oxide  of  zinc  is  added  (about  5  per  cent,  of 
the  sulphate  of  zinc). 

"The  liquor  is  made  to  boil,  and  the  oxide  of  zinc 
takes  the  place  of  the  copper  and  iron,  which  are  pre- 
cipitated. An  equivalent  proportion  of  sulphate  of 
zinc  is  thus  formed.  As  a  test,  a  small  quantity  of 
the  liquor  is  filtered,  and  a  few  drops  of  a  solution  of 
yellow  prussiate  of  potassa  are  added  to  it.  If  the 
precipitate  be  white,  there  is  enough  of  oxide  of  zinc; 
on  the  other  hand,  a  precipitate  which  becomes  bluish 
by  the  contact  of  the  air  shows  the  presence  of  iron, 
and  the  liquor  is  to  be  boiled  again  with  a  fresh  addi- 
tion of  oxide  of  zinc. 

"  After  ascertaining  that  the  liquor  no  longer  con- 
tains iron  or  copper,  it  is  filtered  into  tubs  having 
holes  at  difierent  heights.  Ammonia,  or  better  still, 
carbonate  of  soda,  is  added  until  there  is  formed  a 
slight  precipitate  of  oxide  or  carbonate  of  zinc.  This 
operation  is  absolutely  necessary  if  we  desire  to  obtain 
pulverulent  chromate  of  zinc,  of  a  fine  yellow  color, 
and  if  the  mother  liquor  is  to  hold  a  minimum  quan- 


390 


MAN^UPACTURE  OF  COLORS. 


tity  of  chromate  of  zinc  and  potassa.  Without  this 
precaution,  and  since  the  sulphate  of  zinc  is  always 
acid,  there  is  formed  a  bichromate  of  potassa  which 
does  not  react  upon  the  sulphate  of  zinc. 

"  The  proportions  which  we  find  to  be  the  best  in 
the  preparation  of  the  chromate  of  zinc  are  : — 

"For  the  above  indicated  quantity  of  chromate  of 
soda  and  potassa,  we  need  184.5  kilogrammes  of  sul- 
phate of  zinc.  It  is  not  possible  to  set  down  in  ad- 
vance the  proportions  of  ammonia  or  carbonate  of 
soda  ;  they  are  added  until  there  is  formed  a  precipi- 
tate of  oxide  or  of  carbonate  of  zinc. 

"The  solution  of  double  chromate  is  poured  into 
that  of  zinc,  as  long  as  a  precipitate  takes  place,  and 
the  mixture  is  kept  stirred  with  a  wooden  board. 
After  settling,  the  liquor  is  decanted  and  is  quite 
yellow.  It  is  then  evaporated  to  about  one-third  of 
its  former  bulk,  and  saturated  with  35.35  kilogrammes 
of  soda  crystals.  A  new  quantity  of  chromate  of 
z-inc  is  obtained.  The  supernatant  liquors  are  still 
colored  yellow,  and  saved  for  a  purpose  which  we 
shall  indicate  further  on. 

"The  chromate  of  zinc  is  washed  two  or  three 
times  in  the  tubs,  by  decantation,  and  with  pure 
water  or  rain  water.  The  washings  are  mixed  with 
the  previously  saved  mother  liquors.  The  clear  paste 
of  chromate  of  zinc  is  drained  upon  cloth  filters,  and 
is  there  washed  two  or  three  times.  When  it  has 
acquired  the  proper  consistency  it  is  moulded  into 
the  shape  of  troches,  which  are  dried  in  a  stove-room. 

"  The  washings  and  mother  liquors  are  heated  and 
treated  with  hydrosulphuric  acid,  which  decomposes 
the  chromates  of  potassa  and  zinc  held  in  solution. 
There  is  produced  a  precipitate  which  is  a  compound 


YELLOW  COLORS.  391 

of  hydrated  oxide  of  chrome,  and  of  oxide  and  sul- 
phide of  zinc.  This  compound  may  be  used  in  paint- 
ing as  a  very  fast  and  durable  pigment ;  but  its 
nature  and  hue  may  be  changed  by  a  calcination  and 
washing. 

"  This  product  may  be  obtained  directly  in  the  an- 
hydrous state  by  evaporating  the  liquors  to  dryness, 
powdering  the  residuum,  mixing  it  with  18  per  cent, 
of  sublimed  sulphur,  and  calcining  the  mixture  until 
the  sulphur  is  volatilized.  The  hot  substance  is  then 
thrown  into  water,  and  the  anhydrous  pigment  is 
collected  upon  a  filter. 

"  The  neutral  chromate  of  potassa  and  soda  may 
be  replaced  by  the  neutral  chromate  of  soda,  which 
is  prepared  by  the  calcination  of  chrome  ore  with 
nitrate  of  soda."^ 

2.   Chromate  of  Baryta, 
"  Basing  ourselves  upon  the  processes  which  we 

*  Mr.  R.  Wagner  has  made  the  analysis  of  several  samples  of 
chromate  of  zinc,  and  reports  them  as  follows  in  his  annual  of 
technological  chemistry  (1861)  : — 

Zinc  yellow  from  England — 


Chromic  acid  14.94 

Oxide  of  zinc  15.35 

Carbonic  acid  .3.61 

Water   .  6.19 


100.09 

The  zinc  yellows  prepared  in  Germany  are  generally  adulterated 
with  the  carbonate  or  the  sulphate  of  baryta,  as  is  demonstrated 


by  the  following  analyses  : — 

a.  b. 

Chromic  acid   11.88  9.21 

Oxide  of  zinc  45.78  61.47 

Sulphate  of  baryta  ....    42.34  29.32 


100.00  100.00 


392 


MANUFACTURE  OF  COLORS. 


have  indicated  for  the  manufacture  of  the  chromate 
of  zinc,  and  procuring  a  chloride  of  barium  free  from 
iron,  and  the  neutral  chromate  of  potassa  and  soda, 
we  employ  the  following  formula : — 

"100  kilogrammes  of  chloride  of  barium  are  pre- 
cipitated by  82  to  84  kilogrammes  of  neutral  chro- 
mate of  potassa  and  soda.  The  product  is  washed 
by  decantation,  and  dried  in  a  stove-room. 

"  Such  is  the  process  by  which  we  have  been  en- 
abled to  produce,  in  an  economical  manner,  the  chro- 
mate of  baryta  which  up  to  the  present  day  had  re- 
mained a  product  of  the  experimental  laboratory. 

3.  Orange-red  Sulphide  of  Antimony. 

"  The  preparation  of  this  sulphide,  by  the  processes 
which  we  are  going  to  describe,  results  in  a  color  not 
yet  employed  in  painting,  and  which  is  not  altered  by 
dampness,  light,  or  sulphuretted  hydrogen.  This 
product  and  its  mode  of  preparation  are  new,  and  are 
a  valuable  addition  to  the  new  system  of  painting 
with  zinc  pigments. 

"  One  part  of  natural  sulphide  of  antimony  is 
powdered  and  dissolved  with  the  aid  of  heat,  in  seven 
parts  of  hydrochloric  acid  at  20°  Be.,  which  should 
be  chosen  free  from  lead.  The  sulphuretted  hydrogen 
disengaged  from  the  first  operation  is  condensed  in  a 
milk  of  lime ;  that  of  subsequent  operations  is  em- 
ployed for  preparing  the  sulphide  of  antimony  as 
follows : — 

"  When  all  the  sulphide  is  dissolved,  the  solution 
of  acid  chloride  of  antimony  is  decanted  into  stone- 
ware vessels  which  have  holes  at  different  heights. 
The  liquor  is  diluted  with  pure  water  until  it  begins 
to  become  turbid,  and  a  white  precipitate  appears. 


YELLOW  COLORS. 


393 


The  whole  is  then  put  into  demijohns  and  submitted 
to  a  stream  of  sulphuretted  hydrogen. 

"  We  must  not  forget  to  mention  that  the  glass 
tubes  dipping  into  the  antimonial  solution  should  be 
large,  so  as  not  to  be  obstructed  by  the  red  sulphide 
of  antimony,  formed  by  the  reaction  of  the  sul- 
phuretted hydrogen  with  the  acid  chloride  of  anti- 
mony. The  liquor  should  be  stirred  often  with  a 
wooden  stick,  and  the  vases  covered  or  communi- 
cating several  together,  in  order  not  to  lose  the  sul- 
phuretted hydrogen,  which  may  injure  the  workmen. 
On  that  account  the  last  tubes  dip  into  a  milk  of 
lime  which  condenses  the  excess  of  gas.  The  stream 
of  sulphuretted  hydrogen  is  arrested  when  the  satu- 
ration is  complete,  and  the  precipitate  is  allowed  to 
settle.  The  deposit  of  sulphide  of  antimony  is 
washed  several  times  by  decant ati on,  poured  upon 
filters,  and  again  washed  until  the  water  runs  without 
taste.  The  pigment  is  then  dried  in  the  stove-room 
at  a  moderate  temperature,  which  should  not  be  above 
40°  to  50°,  otherwise  the  sulphide  will  lose  its  com- 
bined water  and  turn  black. 

"  This  mode  of  preparing  the  hydrated  sulphide  of 
antimony  is  a  new  process  of  manufacture,  since  no 
practical  indication  of  the  same  is  to  be  found  in 
works  on  chemistry. 

4.  Mixed  or  Compound  Colors. 

"  We  give  this  name  to  pigments  of  different  tones 
and  hues  obtained  by  the  combination  or  mixture  of 
the  colors  here  described  with  other  usual  colors,  ex- 
cepting those  with  a  lead  or  a  copper  basis. 

"  We  understand  that  with  the  chromate  and  the 
oxide  of  zinc,  with  the  chromate  of  baryta  and  the  red 


394 


MANUFACTURE  OF  COLORS. 


sulphide  of  antimony,  mixed  or  combined  with  other 
usual  colors,  it  is  possible  to  obtain  a  great  many  vari- 
eties of  tones  and  hues  which  will  not  be  acted  upon 
by  sulphuretted  hydrogen.  We  cannot  here  give  a 
complete  nomenclature ;  we  shall,  however,  mention 
the  following  yellows  :  Roman  yellow,  bright  yellow, 
antimony  yellow,  Mars  yellow,  Indian  yellow,  Naples 
yellow,  mineral  yellow,  and  several  chrome  yellows. 

"  All  of  these  colors  may  be  obtained  by  the  com- 
bination of  our  new  products,  and  in  certain  cases 
with  the  aid  of  raw  Sienna. 

"  The  greens  known  under  the  names  of  dark  Eng- 
lish green,  light  English  green,  Milori  green,  green 
earth,  and  verdigris,  are  prepared  in  the  same  manner 
as  the  yellows,  and  with  the  addition  of  a  greater  or 
less  proportion  of  blue. 

"  The  colors  are  mixed  either  in  the  pasty  state  and 
before  being  dried,  or  after  they  have  been  ground. 

"  We  see  that  the  principle  of  these  compound 
colors  consists  in  the  mixture  of  zinc  white  with  the 
new  colors  we  have  just  described,  or  with  other 
usual  colors  which  are  not  altered  by  sulphuretted 
hydrogen.  We  also  arrive  at  tones  and  hues  which 
formerly  could  not  be  obtained  without  the  use  of 
pigments  with  bases  of  lead  and  copper,  so  easily 
acted  upon  by  certain  destructive  agents. 

"  In  a  preceding  description  of  the  yellow  chro- 
mate  of  zinc,  we  said  that  it  was  obtained  by  the 
reaction  of  a  neutral  chromate  of  potassa  and  soda 
upon  a  pure  and  neutral  sulphate  of  zinc.  The  fol- 
lowing are  new  processes  for  the  manufacture  of  a 
basic  chromate  of  zinc. 

"  About  50  kilogrammes  of  pure  oxide  of  zinc  are 
thrown  into  a  solution  of  100  kilogrammes  of  bi- 


YELLOW  COLORS. 


395 


chromate  of  potassa  in  400  kilogrammes  of  hot  water. 
After  boiling,  the  liquor  is  left  to  cool  off,  and,  after 
decantation,  the  precipitate  is  washed  and  dried. 

5.  Lemon  Yellow. 
"  The  above  decanted  liquors  and  washings  are 
evaporated  to  two-thirds  of  their  bulk,  and  receive  a 
solution  of  sulphate  or  of  any  other  soluble  salt  of 
zinc,  in  proportion  variable  with  the  tone  desired. 
The  precipitate,  after  decanting,  is  washed,  etc. 

6.  Pale  Yelloiv. 

"  In  order  to  utilize  all  the  raw  materials,  the  liquors 
from  the  above  operation  are  saved  and  boiled  with  a 
sulphate  of  zinc,  prepared  with  15  kilogrammes  of 
zinc  oxide  and  7  kilogrammes  of  commercial  sul- 
phuric acid.    The  precipitate  is  treated  as  usual. 

"  We  have  also  said  that  compound  greens  were 
prepared  by  the  action  of  sulphuretted  hydrogen  or 
sulphur  upon  the  chromate  of  zinc  remaining  soluble 
in  the  mother  liquors  and  washings ;  and  that  various 
tones  and  hues  were  obtained  by  adding  to  the  chro- 
mate of  zinc  a  greater  or  a  less  proportion  of  blue. 

"We  also  state  that  these  greens  may  be  obtained 
from  a  solution  of  chloride  of  zinc  to  which  is  added 
a  suitable  quantity  of  blue  liquid  or  paste,  or  the  ma- 
terials forming  Prussian  blue.  In  this  manner  the 
green  is  directly  obtained." 

§  12.  Basic  chromate  of  tin,  mineral  laJce. 

Mineral  lake,  which  is  a  combination  of  chromic 
acid  with  the  oxide  of  tin,  possesses  a  fine  lilac  color, 
and  is  sought  for  as  a  substitute  for  vegetable  lakes 
in  the  fabrication  of  paper  hangings  and  for  oil 
painting. 


396 


MA^^^UFACTURE  OF  COLORS. 


This  lake  is  prepared  by  dissolving  the  neutral 
chromate  of  potassa  in  five  or  six  times  its  weight  of 
water,  and  pouring  into  it  a  solution  of  bichloride  of 
tin  as  long  as  a  precipitate  is  formed,  which  is  after- 
wards washed  and  collected  upon  a  filter.  When  the 
chromate  of  tin  is  well  drained,  but  still  wet,  it  is 
ground  with  half  of  its  volume  of  nitrate  of  potassa, 
and  the  whole  is  allowed  to  dry.  The  mass  is  then 
finely  pulverized  and  thrown  by  small  quantities  at 
a  time  into  a  crucible  brought  to  a  low  red  heat,  and 
which  holds  already  some  nitrate  of  potassa.  When 
the  decomposition  is  complete,  the  crucible  is  removed 
from  the  fire,  and  left  to  stand  a  little  while.  The 
supernatant  liquid  nitrate  of  potassa  is  decanted,  and 
the  basic  chromate  of  tin  is  separated  from  the  cru- 
cible by  means  of  hot  water.  It  is  afterwards  washed 
until  the  liquors  have  no  alkaline  reaction. 

The  chromate  thus  obtained  is  of  a  dull  and  pale 
yellow  color,  and  in  order  to  give  it  the  desired  lilac 
hue  it  is  strongly  calcined  for  one  or  two  hours  in  a 
luted  crucible,  placed  in  an  air  furnace  and  covered 
with  coke.  After  this  calcination  the  substance  is 
dense,  and  contains  some  bright  spots.  It  is  easily 
powdered,  and  is  not  acted  upon  by  air,  dampness, 
light,  or  sulphuric  acid. 

Mr.  Malaguti,  to  whom  the  discovery  of  this  lake 
is  due,  prepared  it  by  calcining  at  a  dull-red  heat  and 
in  a  clay  crucible,  an  intimate  mixture  of  100  parts 
of  stannic  acid  (binoxide  of  tin)  and  2  parts  of  oxide 
of  chromium.  After  cooling,  the  vitrified  mass  was 
powdered,  and  was  of  a  lilac  hue,  but  somewhat  gray- 
ish, as  some  people  said. 


YELLOW  COLORS. 


397 


§  13.  Najples  yellow. 

Many  believe  that  this  yellow,  which  is  a  peculiar 
combination  of  oxide  of  lead  and  antimonic  acid,  is 
extracted  from  the  lava  of  Mount  Yesuvius.  Fou- 
geroux  de  Bondaroy  claims  that  Naples  yellow  is  a 
composition  known  at  ^^aples  under  the  name  of 
giallolini,  the  secret  of  which  is  held  by  one  indi- 
vidual. He  adds,  that,  having  been  unable  to  dis- 
cover the  secret  during  his  travels  in  Italy,  his 
chemical  researches  proved  to  him  that  this  yellow 
was  prepared  with  white  lead,  alum,  and  diaphoretic 
antimony  (antimoniate  of  potassa).  In  regard  to 
Naples  yellow,  Th6nard  says :  "  The  preparation  of 
this  yellow  is  well  known  only  to  those  who  make  it 
for  the  arts.  It  is  said  to  be  obtained  by  calcining,  at 
the  proper  temperature,  a  mixture  of  pure  litharge, 
hydrochlorate  of  ammonia  (sal  ammoniac),  diapho- 
retic antimony  (a  combination  of  peroxide  of  anti- 
mony and  potassa),  and  alum." 

Naples  yellow  is  obtained  by  processes  differing 
one  from  another,  and  which  very  likely  furnish 
different  tones  of  color. 

Fougeroux  de  Bondaroy  has  indicated  the  follow- 
ing recipe : — 

White  lead  24  parts. 

Diaphoretic  antimony  (antimoniate  of  potassa)   4  parts. 

Sal  ammoniac  1  part. 

Alum  1  part. 

All  of  these  substances  should  be  finely  powdered 
and  throughly  mixed  before  they  are  placed  in  a  cru- 
cible which  is  kept  at  a  red  heat  for  three  hours. 
After  cooling,  the  crucible  is  broken,  and  the  mass 


398 


MANUFACTURE  OF  COLORS. 


which  is  very  dense  and  compact,  and  of  a  fine  yel- 
low color,  is  finely  ground,  and  then  washed  several 
times  for  the  purpose  of  separating  the  soluble  sub- 
stances.   Lastly,  the  powder  is  dried. 

Naples  yellow  is  also  obtained  by  smelting,  at  a 
low  temperature,  3  parts  of  massicot  and  1  part  of 
oxide  of  antimony. 

Two  parts  of  red  lead  may  also  be  fused  with  3 
parts  of  powdered  metallic  antimony  and  1  part  of 
calamine. 

Another  recipe  consists  in  smelting  5  to  6  parts  of 
lead,  2  to  4  parts  of  antimony,  and  1  part  of  cream 
tartar  (bitartrate  of  potassa). 

Again  it  is  said  that  16  parts  of  lead,  16  of  anti- 
mony, 2  of  cream  tartar,  and  1  of  common  salt,  pro- 
duce a  Naples  yellow. 

Five  parts  of  litharge,  two  of  antimoniate  of  potassa, 
and  one  of  sal  ammoniac,  give  a  fine  yellow. 

Lastly,  Mr.  Guimet,  of  Lyons,  asserts  that  a  hand- 
some yellow  maybe  produced  with  two  parts  of  red 
lead  and  one  part  of  antimoniate  of  potassa. 

A  German  chemist,  Mr.  Brunner,  has  made  a  spe- 
cial study  of  Naples  yellow,  and,  after  a  great  many 
experiments,  finds  that  the  finest  article  is  prepared 
in  the  following  manner : — 

One  part  of  tartrate  of  potassa  and  antimony  or 
tartar  emetic,  purified  by  several  crystallizations,  is 
intimately  mixed  with  two  parts  of  nitrate  of  lead 
free  from  copper  or  iron,  and  four  parts  of  common 
salt.  The  homogeneous  mixture  is  slowly  brought 
to  a  state  of  fusion  in  a  Hessian  crucible.  After  cool- 
ing, the  mass  is  detached  by  striking  the  overturned 
crucible,  and  then  ground  and  washed,  in  order  to 


YELLOW  COLORS. 


399 


remove  the  salt  which  formed  the  upper  layer  of  the 
melted  mass. 

The  yellow  is  very  fine  with  a  properly  conducted 
fire,  but  too  much  heat  impairs  it.  The  color  may  be 
brightened  by  washings  with  hydrochloric  acid. 

Mr.  A.  Hick,  in  the  Technologiste^  vol.  xxi.  page 
72,  has  indicated  a  mode  of  preparing  a  yellow  color 
which  resembles  I^aples  yellow. 

It  is  known,  says  he,  that  in  refining  lead  the  metal  is 
melted  in  a  reverberatory  furnace,  and  presents  a  large 
surface  to  the  action  of  the  air.  The  antimony  and 
other  metals  usually  accompanying  lead  are  oxidized, 
and  their  oxides  form  a  sort  of  scoria  on  top  of  the 
fused  lead.  These  oxides  are  principally  those  of 
lead,  antimony,  and  arsenic;  and  in  order  to  trans- 
form them  into  a  pigment,  they  are  finely  ground,  and 
calcined  in  a  reverberatory  furnace,  or  in  any  other 
furnace  where  they  are  simultaneously  acted  upon  by 
air  and  heat.  The  calcination  is  begun  at  a  low  tem- 
perature, which  is  slowly  raised  to  a  red  heat.  The 
length  of  the  operation  depends  on  the  quantity  of 
material  operated  upon,  and  in  practice,  from  one  to 
three  days  are  necessary  to  calcine  1500  kilogrammes 
of  pulvei'ized  oxides. 

It  is  advantageous  to  mix  with  the  powder,  during 
the  latter  period  of  the  calcination,  a  certain  quantity 
of  common  salt  (chloride  of  sodium).  An  accurate 
proportion  of  salt  is  not  very  important,  but  practice 
indicates  about  one-half  of  the  weight  of  the  oxides. 

The  calcined  product  is  sometimes  saturated  with 
sulphuric,  hydrochloric,  or  acetic  acid,  or  exposed  to 
the  vapors  of  acetic  acid  in  tan  beds,  like  those  used 
for  white  lead.  This  treatment  with  common  salt  and 
acids  improves  the  quality  of  the  color. 


400 


MAI^UFACTUEE  OF  COLORS. 


When  the  color  remains  constant  in  the  furnace, 
the  oxides  are  removed,  washed,  ground,  etc.* 

The  color  of  Naples  yellow  varies  in  tone  with  the 
different  processes  of  manufacture,  but  generally  it 
possesses  brightness,  depth,  and  durability.  This 
pigment  unites  readily  with  other  colors,  and  enhances 
the  brightness  of  the  yellow  ochre  with  which  it  is 
sometimes  mixed.  Its  preparation  requires  peculiar 
precautions;  for  instance,  it  should  be  ground  upon  a 
slab  of  porphyry  or  marble,  and  collected  with  an 
ivory  blade,  because  steel  turns  it  green.  It  is  used 
on  chamois  grounds,  for  fine  yellows  imitating  gold, 
and  for  carriages. 

§  14.  Cadmium  yellow. 

This  salt  is  of  a  remarkably  fine  orange-yellow 
color,  which  remains  unchanged  by  fire.  It  fuses  at 
a  white  heat,  and  by  cooling,  it  crystallizes  into  trans- 
lucent and  micaceous  laminae  possessing  a  magnifi- 
cent lemon-yellow  color.  On  account  of  its  beauty 
and  durability,  this  pigment  is  used  in  artistic  paint- 
ings, but  its  price  is  still  very  high. 

Cadmium  yellow  is  obtained  by  passing  a  stream 
of  sulphuretted  hydrogen  through  a  solution  of 
nitrate  or  sulphate  of  cadmium.  The  precipitate 
of  sulphide  of  cadmium  is  washed,  collected  upon 
a  filter,  and  dried  in  a  stove-room.    Thus  prepared, 

*  The  above  described  process  is  evidently  an  economical  method 
for  obtaining  a  color  nearly  identical  with  Naples  3^ellow,  that  is, 
an  antimoniate  of  lead,  the  degree  of  saturation  of  which  is  little 
known.  It  is  possible  that  the  small  proportion  of  arsenic  con- 
tained in  the  oxides,  modifies  the  tone  of  the  color,  and  causes  a 
certain  difference  between  it  and  real  Naples  yellow  ;  but  then  the 
pigment  is  poisonous,  and  should  be  used  very  carefully. 


YELLOW  COLORS. 


401 


the  yellow  is  in  the  state  of  impalpable  powder  which 
covers  very  well. 

This  color  may  also  be  prepared  in  the  dry  way,  by 
heating  in  a  crucible  oxide  of  cadmium  with  an  excess 
of  sublimed  sulphur.  The  yellow  prepared  in  this 
manner  is  not  so  handsome  as  the  previous  one,  and 
does  not  cover  so  well. 

Blue  pigments  and  cadmium  yellow  produce  very 
rich  and  durable  greens,  which  should  not  be  mixed 
with  white  lead  or  other  lead  compounds,  because  the 
latter  are  decomposed  and  blackened  by  the  sulphur 
of  the  cadmium. 

§  15.  Yellow  of  antimony  and  zinc, 

Messrs.  G.  Hallett  and  J.  Stenhouse,  in  1861,  took 
out  a  patent  in  England,  for  the  manufacture  of  colors 
with  an  antimonial  basis.  The  following  is  their 
mode  of  operation  v — 

They  take  the  native  oxide  of  antimony,  or  the 
mixed  oxide  and  sulphide,  often  associated  with  the 
gray  sulphide  of  antimony.  It  is  a  combination  in 
variable  proportions  of  antimony  and  oxygen,  with 
more  or  less  sulphide  of  antimony,  oxide  of  iron,  silica, 
water,  and  sometimes  arsenic,  and  the  color  of  which 
varies  from  a  light  yellow  to  a  yellowish-red.  The 
gangue  is  removed  as  far  as  practicable,  by  pick- 
ing and  washing,  and  the  ore  is  finely  ground  and 
sifted.  The  powder  is  introduced  into  large  cruci- 
bles, muffles,  or  reverberatory  furnaces,  where  it  is 
carefully  calcined  at  a  dull  red  heat  and  with  the 
access  of  the  air.  The  mass  is  constantly  stirred  in 
order  to  prevent  too  great  an  elevation  of  its  tempera- 
ture. During  the  operation  the  powder  emits  steam, 
sulphur,  and  sulphurous  acid,  fumes  of  antimony  and 
26 


402 


MANUFACTURE  OF  COLORS. 


arsenic,  and  becomes  less  fusible.  The  calcination 
lasts  generally  from  two  to  three  hours,  and  is  com- 
pleted when  vapors  and  fumes  are  no  longer  disen- 
gaged, and  when  all  the  antimony  has  been  trans- 
formed into  anhydrous  antimonious  acid. 

The  impure  antimonious  acid  thus  produced,  is 
reduced-  to  an  impalpable  powder  by  grinding  and 
levigation.  After  drying,  it  forms  with  oil,  varnish, 
etc.,  a  new  pigment  for  painting,  which  may  be  com- 
bined with  other  oxides  or  salts,  such  as  zinc  oxide, 
white  lead,  chromate  of  lead. 

A  yellow  color  is  produced  with  eight  parts  of 
native  oxide  of  antimony,  or  of  oxide  mixed  with  sul- 
phide, or  the  impure  antimonious  acid  obtained  by  the 
above  process,  three  parts  of  red  lead  or  litharge,  and 
one  part  of  oxide  of  zinc.  The  whole  is  finely  pow- 
dered and  thoroughly  mixed,  and  calcined  in  crucibles, 
muffles,  or  furnaces,  until  the  combination  is  effected 
and  the  yellow  color  has  appeared.  The  mass  is  then 
finely  powdered,  and  ground  in  oil  or  in  varnish. 

The  above  proportions  give  good  results,  but  they 
may  be  made  to  vary.  Sometimes  the  proportion  of 
oxide  of  lead  is  increased ;  at  other  times,  the  oxide 
of  zinc  is  suppressed.  About  four  parts  of  common 
salt  may  be  employed,  in  which  case  the  product  is 
afterwards  carefully  washed.  By  varying  the  propor- 
tions of  the  constituent  parts,  as  seen  in  the  examples 
below,  various  tones  and  hues  of  Naples  yellow  will 
be  produced : — 


I. 


II. 


III. 


Antimonious  acid 
Oxide  of  lead  . 
Oxide  of  zinc  . 


4  parts 

2 

1 


1 
2 
1 


3 
3 
1 


YELLOW  COLORS. 


403 


IV. 


V. 


VI. 


Antimonious  acid 
Oxide  of  lead 
Oxide  of  zinc 


1  part 

1 

1 


1 
1 


2 
1 


§  16.  Turner  yellow,    Kassler  yellow,    Cassel  yellow, 
MontpelUer  yellow,  Verona  yellow.  Mineral  yellow. 

These  various  names  belong  to  quite  a  number  of 
colors,  the  composition  of  which  is  not  perfectly  es- 
tablished. Nevertheless  they  appear  to  result  fi-om 
the  combination  of  a  protochloride  of  lead  with  vari- 
able proportions  of  oxide  of  lead. 

According  to  Hahneman,  the  mineral  yellow  of 
Turner  is  prepared  by  mixing  together  twenty-one 
parts  of  red  lead,  and  two  parts  of  sal  ammoniac 
(hydrochlorate  of  ammonia).  After  fusion  in  a  cruci- 
ble, the  mass  is  poured  upon  a  marble  slab,  and  then 
pulverized. 

Other  persons  prepare  this  color  by  fusing  litharge 
or  white  lead  with  common  salt  or  sal  ammoniac. 
The  following  is  the  method  practised  at  Montpellier 
by  Chaptel,  and  described  by  him : — 

Four  parts  of  finely  pulverized  litharge  are  put  into 
a  stoneware  vessel,  and  mixed  with  a  portion  of  a 
solution  of  one  part  of  common  salt  in  four  parts  of 
water.  The  stirring  is  effected  with  a  spatula  of 
glass,  lead,  or  wood,  but  iron  is  discarded.  The  sub- 
stance swells  and  becomes  hard ;  it  is  then  broken 
and  mixed  with  another  portion  of  the  saline  solution. 
The  stirring  is  continued  with  fresh  additions  of  the 
solution.  "When  the  latter  is  exhausted,  pure  water 
is  used  as  long  as  the  substances  continue  to  swell. 
At  last  they  sink  down.  The  stirring  is  continued, 
and  when  the  mass  has  become  perfectly  white, 


404 


MANUFACTURE  OF  COLORS. 


smooth,  and  fine,  it  is  thoroughly  washed  in  water. 
The  paste  is  then  pressed  in  a  cloth,  and  afterwards 
distributed  in  shallow  stoneware  vessels  which  are  ex- 
posed to  a  moderate  but  protracted  heat.  The  dome 
of  a  porcelain  furnace  is  well  adapted  to  this  last 
operation.  The  cooling  is  slow,  and  the  result  is  a 
chamois  yellow  of  a  pure  hue,  but  not  so  bright  as 
ifaples  yellow. 

Mineral  yellow  is  produced  by  a  mixture  of 
English  litharge  and  sal  ammoniac ;  its  color  is  a 
bright  lemon-yellow  without  durability.  It  is  pre- 
pai'ed  with  two  or  three  parts  of  English  litharge 
(yellow  protoxide  slightly  vitrified),  and  one  part  of 
sal  ammoniac,  ground  together  in  a  marble  mortar 
with  a  little  water.  The  resulting  paste  is  put  into 
an  unglazed  clay  dish,  which  is  heated  in  a  reverbe- 
ratory  furnace,  slowly  at  first  to  evaporate  the  water. 
The  heat  is  then  increased  by  degrees  until  the  am- 
monia has  entirely  escaped.  The  dish  is  removed 
from  the  furnace,  and  the  color  is  of  a  bright  lemon- 
yellow.  It  is  employed  mostly  for  coach  painting 
and  theatrical  scenery. 

Mr.  Merimee  says  that  a  more  durable  mineral 
yellow  is  prepared  by  grinding  separately  and  mixing 
afterwards  : — 

Metallic  bismuth  3  parts. 

Sulphide  of  antimony  24  " 

Nitrate  of  potassa   64  " 

The  mixture  is  introduced  b}^  degrees  into  a  heated 
crucible.  After  fusion,  the  substances  are  thrown 
into  water  and  stirred  as  long  as  it  is  necessary.  The 
precipitate  is  washed  by  decantation  until  the  water 
is  tasteless,  whence  it  is  collected  upon  a  filter  and 
well  dried.    The  resulting  oxide  is  in  the  shape  of  a 


YELLOW  COLORS. 


405 


fine  powder  colored  a  dirty  yellow.  One-eighth  of  one 
part  of  this  dry  oxide  is  mixed  with  one  part  of  hydro- 
chlorate  of  ammonia,  and  sixteen  parts  of  pure  lith- 
arge, and  the  whole  is  fused  in  the  manner  previously 
indicated.  Should  a  given  tone  of  color  be  desired, 
it  is  necessary  that  the  degree  of  temperature  and  the 
length  of  operation  should  always  be  exactly  the  same. 

There  are  other  processes  for  preparing  this  color. 
For  instance,  there  are  manufacturers  who  produce  it 
by  maintaining  for  some  time  and  exposed  to  the 
access  of  the  air,  a  neutral  chloride  of  lead  in  fusion. 
This  salt  is  partly  decomposed;  chlorine  is  disen- 
gaged, and  the  reduced  metal  combines  with  the  un- 
decomposed  chloride  of  lead. 

Others  prefer  melting  together  one  part  of  chloride 
of  lead  and  four  parts  of  red  lead. 

Lastly,  some  persons  heat  ten  parts  of  massicot  and 
one  part  of  sal  ammoniac.  The  molten  mass  is  divided 
into  two  layers,  the  lower  one  being  metallic  lead, 
and  the  upper  one,  a  pure  and  bright  mineral  yellow. 

This  color  is  somewhat  difficult  of  preparation,  and 
great  cleanliness  is  necessary.  Many  tones  and  hues 
are  to  be  found  in  the  trade  depending  on  the  pro- 
portion of  basic  chloride.  But  in  every  case,  it  may 
be  deepened  by  a  second  fusion,  or  lightened  by  a 
fusion  with  a  small  proportion  of  sal  ammoniac. 

It  is  employed  espe.cially  for  coach  and  theatrical 
painting,  and  the  color  is  deepened  by  an  addition  of 
chrome  yellow.  It  should  not  be  placed  in  contact 
with  sulphur  compounds. 

The  Merimee  yellow  is  very  rich  of  tone,  and  very 
durable.  It  is  sought  for  artistic  painting,  and  is 
sold  in  the  trade  under  the  names  of  antimony  yellow 
and  superfine  mineral  yellow. 


406 


MANUFACTURE  OF  COLORS. 


§  17.  Mineral  straw-yellow. 

This  very  bright  color  may  be  considered  as  a  basic 
sulphate  of  lead  (a  combination  of  sulphuric  acid  with 
an  excess  of  oxide  of  lead).  It  is  obtained  by  melting 
in  a  crucible  a  mixture  of  equal  parts  of  sulphate  of 
lead  and  litharge.  After  fusion,  the  mixture  is  poured 
out  upon  a  slab,  and  when  cold  it  is  powdered. 

The  pure  mineral  straw-yellow  possesses  a  finely 
toned  yellow  color,  is  durable,  and  covers  well.  But 
it  should  not  be  exposed  to  sulphuretted  gases.  That 
found  in  the  trade  is  very  variable  in  tone,  on  account 
of  the  large  proportion  of  lead  introduced  into  it. 

§  18.  Mineral  turhith. 

The  names  of  mineral  yellow  and  mineral  turhith 
are  given  to  a  subsulphate  of  mercury,  which  is  pre- 
pared as  follows  :— 

One  part  of  mercury  is  boiled  with  two  parts,  at 
least,  of  sulphuric  acid  at  66°  Be.,  in  a  stoneware 
retort  heated  in  a  covered  furnace.  There  is  an 
abundant  production  of  sulphurous  acid,  and,  when 
the  reaction  is  completed,  the  retort  is  broken,  and  the 
acid  sulphate  of  mercury  is  dissolved  in  boiling  water. 
The  mass  becomes  decomposed,  and,  after  repeated 
washings  with  hot  water,  acquires  a  pretty  lemon- 
yellow  color.  Lastly,  it  is  collected  upon  a  filter  and 
dried.  Mineral  turhith  is  not  much  used,  and  it  is 
said  to  become  decomposed  in  the  air.  This  yellow, 
with  Prussian  blue,  produces  a  magnificent  green, 
finer  than  that  prepared  with  orpiment,  and  without  a 
tendency  to  become  black.    It  is  highly  poisonous. 


YELLOW  COLORS. 


407 


§  19.  Orjpin  or  orpiment.    Yellow  sulphide  of  arsenic. 
Yellow  realgar. 

This  mineral,  which  is  a  trisiilphide  of  arsenic,  has 
a  fine  gold-yellow  color,  and  is  in  the  shape  of  a  mass 
of  soft  and  flexible  laminae,  semi-translucent,  and 
easily  separated,  also  in  oblique  prisms.  It  is  taste- 
less, odorless,  and  presents  a  lamellar  fracture.  More 
fusible  than  arsenic,  it  burns  with  a  blue  flame  and 
produces  a  garlic  smell.  This  mineral  is  composed 
of— 

Arsenic  63.98 

Sulphur   .       .       .       .       .       .  36.02 

100.00 

It  cannot  be  combined  with  pigments  holding 
lead  or  certain  other  metallic  compounds,  because  it 
blackens  them. 

Orpiment  is  found  in  the  natural  state  often  mixed 
with  realgar  or  bisulphide  of  arsenic  in  secondary 
formations,  but  not  in  sufficient  quantity  for  the  arts. 
It  is  found  in  Hungary,  Styria,  Suabia,  Bohemia, 
Walachia,  the  East,  Peru,  etc. 

Artificial  orpiment,  or  yellow  sulphide  of  arsenic, 
has  properties  somewhat  difterent  from  those  of  the 
natural  article.  It  appears  to  be  a  mixture  of  96 
parts  of  arsenious  acid  and  6  parts  of  sulphide  of 
arsenic.    The  following  is  its  mode  of  fabrication  : — 

1  part  sublimed  sulphur,  finely  powdered,  and 
passed  through  a  silken  sieve,  is  thoroughly  mixed 
with  2  parts  of  powdered  arsenious  acid.  The  mix- 
ture is  introduced  into  a  crucible  which  is  covered 
with  another  crucible,  or,  better  still,  with  a  condenser 
for  collecting  the  sublimate.   The  latter  is  an  opaque 


408 


MANUFACTURE  OF  COLORS. 


mass,  the  color  of  which  varies  from  a  clear  yellow  to 
a  red,  according  to  the  manner  in  which  the  fire  has 
been  conducted,  or  the  greater  or  less  thoroughness  in 
the  mixing  of  the  sulphur  and  arsenic.  By  varying 
the  proportions  of  sulphur,  and  conducting  the  opera- 
tion with  more  or  less  rapidity,  all  the  intermediary 
tones  and  hues  between  the  extreme  colors  may  be 
obtained. 

Orpiment  is  an  extremely  poisonous  color,  which 
requires  great  precautions  in  its  preparation  and 
handling.  Moreover  it  is  not  durable.  It  is  em- 
ployed especially  in  oil  painting,  and  produces  with 
Prussian  blue  a  handsome  green,  which  is,  however, 
liable  to  turn  black. 

The  name  of  royal  yellow  is  sometimes  given  to  a 
sulphide  of  arsenic  obtained  by  precipitation  in  the 
wet  way. 

Mr.  K.  Wagner  says  that  an  extremely  fine  yellow 
orpiment  is  prepared  with  sulphide  of  arsenic  and 
sulphate  of  baryta,  and  might  replace  chrome  yellow 
if  there  were  no  arsenic  in  it.  This  pigment  is  pre- 
pared as  follows : — 

2  parts  of  finely-ground  sulphate  of  baryta  are 
calcined  with  1  part  of  powdered  charcoal,  tar,  or  oil 
waste,  etc.  The  calcined  mass  is  pulverized  again, 
mixed  with  1  part  of  ground  orpiment,  and  boiled  in 
water.  After  filtration  the  liquor  contains  a  sulpho- 
arsenite  of  baryta,  which  may  be  precipitated  by 
diluted  sulphuric  acid.  Chloride  of  barium  may  be 
added  before  the  addition  of  the  acid,  and  in  this 
manner  the  precipitated  pigment  is  lightened  in  color. 

The  disagreeable  and  unhealthy  escape  of  sulphu- 
retted hydrogen  may  be  avoided  by  adding  to  the 
solution  of  chloride  of  barium  a  quantity  of  arseniate 


YELLOW  COLORS. 


409 


of  potassa  in  hydrochloric  acid,  proportional  to  the 
amount  of  sulphuretted  hydrogen  produced. 

§  20.  Arsenite  of  lead, 

Arsenite  of  lead  is  also  a  highly  poisonous  pigment, 
which  is  often  substituted  for  orpiment.  Its  yellow 
color  is  equally  fine  with  it,  more  durable,  and  with  a 
good  body. 

The  arsenite  of  lead  is  obtained  from  an  intimate 
and  finely  powdered  mixture  of  10  parts  of  arsenious 
acid  and  7  parts  of  litharge,  which  is  brought  to  a  red 
heat  in  a  crucible  placed  in  a  furnace  having  a  good 
draft.  When  the  substances  are  in  a  quiet  state  of 
fusion,  they  are  poured  upon  a  marble  and  afterwards 
finely  ground. 

By  varying  the  proportion  of  lead,  i.  6.,  by  increas- 
ing that  of  litharge,  the  arsenites  become  redder, 
especially  if  the  heat  be  more  protracted. 

§  21.  Massicot  Litharge, 

Massicot  is  a  pulverulent  yellow  protoxide  of  lead, 
which  when  fused  is  called  litharge. 

If  metallic  lead  be  placed  upon  the  hollow  hearth 
of  a  reverberatory  furnace  having  a  fireplace  on  two 
opposite  sides,  it  soon  melts  and  becomes  oxidized  on 
the  surface.  By  removing  the  oxidized  portions  a 
new  quantity  of  oxide  is  formed,  and  so  on  until  all 
the  metal  is  transformed  into  a  fine  yellow  protoxide, 
or  massicot.  It  is  sometimes  employed  in  painting, 
and  it  is  more  or  less  reddish  according  as  the  heat 
has  been  more  or  less  raised,  or  the  lead  is  purer,  etc. 

Litharge  is  a  protoxide  of  lead  which  has  been 
melted.    Its  yellow  color  often  acquires  a  reddish 


410 


MANUFACTURE  OF  COLORS. 


hue,  which  is  due  either  to  impurities,  or  to  the  tem- 
perature, or  to  its  more  or  less  sudden  cooling. 

It  is  seldom  that  the  manufacturer  of  pigments  is 
obliged  to  prepare  his  litharge,  which  can  be  had  in 
the  trade  at  moderate  prices,  and  which  results  from 
the  cupellation  of  lead  in  metallurgic  works. 


This  yellow,  which  possesses  the  brightness  of 
orpin  and  of  chromate  of  lead,  is  prepared  by  precipi- 
tating a  solution  of  nitrate  or  acetate  of  lead  with  a 
solution  of  iodide  of  potassium.  The  nitrate  of  lead 
produces  a  brighter  article  than  the  acetate.  Iodide 
of  lead  is  soluble  in  1235  parts  of  cold,  and  192  parts 
of  boiling  water.  The  latter  by  cooling  deposits 
spangles  of  iodide. 

We  are  indebted  to  Mr.  Huraut  for  a  more  practical 
and  economical  method  for  the  manufacture  of  iodide 
of  lead  than  that  generally  practised.  The  following 
is  a  description  of  the  process : — 

Take  of— 


and  make  with  these  substances  a  paste  which  is 
gently  heated  and  continually  stirred.  When  the 
combination  is  effected,  that  is,  when  all  the  iodine 
has  disappeared,  more  water  is  added.  After  settling 
and  decanting,  the  residuum  is  treated  with  a  fresh 
portion  of  water  and  the  mixed  liquors  are  filtered. 
They  hold  iodide  of  calcium,  which  is  decomposed  by 
a  solution  of  152  parts  of  neutral  acetate  of  lead,  or 
of  132  parts  of  nitrate  of  lead.    The  precipitate  is 


§  22.  Iodide  of  lead. 


Iodine 
Iron  filings 
Quicklime 
Water 


sufficient, 


100  parts. 
15  " 
25  " 


YELLOW  COLORS. 


411 


washed  two  or  three  times  only,  and  then  dried  at  a 
moderate  temperature. 

The  above  proportipns  give  175  parts  of  a  micaceous 
iodide  of  lead,  which  is  of  a  magnificant  orange- 
yellow  color. 

This  pigment  is  very  bright,  but  is  aifected  by  the 
sun  and  sulphurous  emanations.   It  is  also  poisonous. 

§  23.  Uranium  yellow. 

Uranium  yellow  is  extracted  from  the  uranium- 
pech-blende  or  pech-urane,  which  was  formerly  dis- 
carded, but  which  at  the  present  time  is  mined  with 
profit  in  Germany,  especially  for  furnishing  glass- 
makers  with  a  pigment  which  colors  glass  a  very 
handsome  greenish-yellow. 

Mr.  Patera  was  the  first  who  proposed  a  manufac- 
turing process,  which  may  be  summed  up  as  follows : 
Powdered  pech-urane  is  mixed  with  chalk,  and  by 
calcination  forms  a  uranate  of  lime  which  is  treated 
by  sulphuric  acid.  The  solution  is  boiled  with  metallic 
iron,  in  order  to  reduce  the  oxide  of  uranium  to  the 
protoxide  state,  and  is  afterwards  largely  diluted  with 
water.  A  basic  sulphate  of  protoxide  of  uranium  is 
precipitated,  and  is  separated  from  the  basic  sulphate 
of  protoxide  of  iron  by  being  dissolved  in  the  smallest 
possible  quantity  of  sulphuric  acid.  An  addition  of 
water  precipitates  it  again.  The  pure  basic  sulphate 
of  protoxide  of  uranium,  thus  obtained,  is  used  for  the 
preparation  of  other  combinations  of  uranium. 

Mr.  Patera  has  since  modified  this  process.  The 
pech-urane  is  calcined  with  lime  in  a  reverberatory 
furnace,  then  treated  by  sulphuric  acid  mixed  with  a 
small  proportion  of  nitric  acid,  which  dissolves  the 
oxide  of  uranium.    To  this  impure  solution  an  excess 


412  MANUFACTURE  OF  COLORS. 


of  carbonate  of  soda  is  added,  which  forms  a  sohible 
carbonate  of  soda  and  of  oxide  of  uranium.  Sulphu- 
ric acid  separates  from  it  an  uranate  of  soda,  which  is 
sold  under  the  name  of  uranium  yellow. 

This  process  is  said  by  Mr.  C.  F.  Anthon,  to  fur- 
nish a  product  which  is  not  very  well  received  in  the 
trade. 

Mr.  Anthon  having  had  to  work  several  tons  of 
pech-urane,  with  a  variable  yield  of  10  to  70  per  cent, 
of  uranic  oxide,  it  is  interesting  to  chemists  to  know 
his  process,  which  presents  several  advantageous 
features. 

The  ore  is  pulverized  as  finely  as  possible,  which  is 
difficult  with  the  poor  qualities.  A  clear  and  liquid 
paste  is  made  with  the  powder  and  water,  which  is 
treated  with  a  mixture  of  equal  parts  of  nitric  and 
hydrochloric  acids.  These  need  not  be  pure,  and 
may  contain  a  certain  proportion  of  sulphuric  acid. 
The  operation  should  take  place  in  the  open  air  or 
under  a  chimney  with  a  good  draft,  and  the  vessels 
used  are  of  varnished  stoneware  of  a  capacity  of  20 
litres  for  12  or  13  kilogrammes  of  powdered  pech- 
urane,  or  of  cast-iron  holding  from  50  to  100  kilo- 
grammes of  ore.  The  materials  are  constantly  stirred, 
as  long  as  there  are  red  vapors  disengaged,  especially 
after  each  addition  of  acids. 

By  a  previous  calcination  of  the  ore,  the  escaping 
acid  fumes  will  be  less  abundant,  and  there  will  be  a 
sensible  saving  of  nitric  acid,  since  aqua  regia  may 
then  be  composed  of  three  parts  of  hydrochloric  acid 
to  one  part  of  nitric  acid.  The  action  of  the  aqua 
regia  is  very  energetic,  even  without  the  aid  of  heat, 
and  especially  when  the  ore  is  not  calcined;  the  pro- 


YELLOW  COLORS. 


413 


duced  heat  is  then  so  great  that  the  ore  is  entirely 
subdivided  and  corroded. 

The  proportion  of  nitric  acid  cannot  be  even  ap- 
proximately determined;  it  depends  entirely  on  the 
very  variable  quality  of  pech-blende  used,  and  whether 
the  ore  is  in  the  raw  state  or  calcined.  At  all  events, 
the  end  of  the  decomposition  is  ascertained  by  the 
absence  of  effervescence  and  of  red  vapor. 

As  soon  as  a  small  addition  of  nitric  acid  fails  to 
produce  a  sensible  reaction,  the  paste,  which  should 
have  been  kept  at  about  the  same  degree  of  consist- 
ency by  the  addition  of  water  if  necessary,  is  then 
evaporated  and  stirred  until  it  appears  dry.  When 
this  point  is  reached,  the  kettle  is  brought  to  about 
a  red  heat,  without  reaching  it,  however. 

The  dried  mass  is  lixiviated  with  water,  and  the 
mixed  liquors,  which  mark  from  8°  to  12°  Be.,  are 
treated  with  carbonate  of  soda,  in  slight  excess,  that 
is,  until  the  latter  substance  can  be  recognized  by  the 
taste.    A  great  excess  is  to  be  avoided. 

The  liquor  thus  obtained  is  not  clear,  and  is  colored 
a  yellowish-brown  by  the  precipitated  oxides.  It  is 
made  to  boil  in  a  cast-iron  kettle,  which  is  afterwards 
allowed  to  cool  very  slowly  until  the  next  morning, 
by  closing  the  flues  and  covering  the  vessel. 

The  next  day,  the  clear  and  yellow  liquor  above 
the  deposit  is  siphoned  otiP.  It  is  a  nearly  pure  so- 
lution of  urano-sodic  carbonate.  The  thick  deposit 
is  drained  in  cloth  sacks  (0.80  metre  long,  and 
0.20  to  0.22  metre  wide),  fixed  to  a  wooden  frame, 
and  which  are  compressed  when  the  liquors  have 
ceased  to  run  naturally.  The  pressed  cake  is  boiled 
again  w^ith  water,  and  a  small  proportion  of  soda,  in 
order  to  extract  what  may  remain  in  it  of  uranium 


414 


MA^J^UFACTURE  OF  COLORS. 


oxide.  All  the  uranic  solutions  are  then  concentrated 
into  a  cast-iron  kettle,  and  the  urano-sodic  carbonate 
which  separates  is  "fished,"  that  is,  collected  in  glazed 
dishes  suspended  in  the  boiling  liquor.  When  the 
deposits  no  longer  take  jDlace,  the  mother  liquors, 
which  still  hold  a  notable  proportion  of  oxide  of  ura- 
nium, are  mixed  with  the  washings  of  the  dried  mass, 
after  the  treatment  by  the  acids. 

The  collected  urano-sodic  carbonate  forms  a  crys- 
talline greasy  powder,  which  is  but  slightly  soluble 
in  water,  and  is  of  a  bright  lemon-yellow  when  pure. 
But  as  this  carbonate  is  not  always  of  constant  com- 
position, or  in  favor  with  the  trade,  it  should  be  changed 
by  a  further  treatment,  into  ammoniacal  uranium 
oxide,  of  a  much  deejDer  yellow,  and  which  is  more 
eagerly  sought  for,  on  account  of  the  greater  propor- 
tion of  uranium  oxide  it  yields. 

The  urano-sodic  carbonate  is  slowly  dissolved  in 
water,  and  the  solution  is  sufficiently  saturated  when 
it  marks  from  15°  to  18°  Be.  The  impurities  are 
separated,  either  by  filtration,  or  by  allowing  the 
liquors  to  stand. 

Although  neither  of  these  operations  is  difficult,  it 
is  preferable  in  practice  to  put  the  raw  urano-sodic 
carbonate  into  small  wooden  tubs  (5  to  6  centimetres 
high,  and  from  20  to  25  centimetres  in  diameter), 
through  which  water  is  made  to  pass  until  all  the  car- 
bonate is  dissolved.  By  this  treatment,  the  foreign 
substances  remain  insoluble. 

The  pure  solution  of  urano-sodic  carbonate  is  poured 
into  a  cast-iron  kettle,  and  is  decomposed  by  solutions 
of  sulphate  or  hydrochlorate  of  ammonia  (according 
to  the  market  value  of  these  salts),  which  are  added 
at  intervals  and  in  quantities  to  be  determined  by 


YELLOW  COLORS. 


415 


experience.  The  operation  is  completed  when  efler- 
vescence  ceases,  or  when  carbonate  of  ammonia  is  dis- 
engaged. The  yellow  ammoniacal  oxide  is  collected 
(fished)  in  dishes,  as  in  the  preparation  of  the  urano- 
sodic  carbonate,  and  is  washed  and  dried. 

When  the  boiling  mother  liquors,  after  the  addition 
of  a  small  quantity  of  ammoniacal  salt,  do  not  give 
a  precipitate,  or  are  without  alkaline  reaction,  they 
are  removed  from  the  fire  and  preserved  for  another 
operation  with  the  washings,  since  they  yet  hold  a 
certain  proportion  of  oxide  of  uranium. 

The  proportion  of  ammoniacal  salts  employed  is 
small,  because  enough,  and  no  more,  is  added  for  the 
acid  of  the  salt  to  saturate  the  soda  of  the  carbon- 
ate. As  the  anhydrous  urano-sodic  carbonate  con- 
tains 22.9  per  cent,  of  soda,  100  parts  of  it  require  49 
parts  of  hydrochlorate  of  ammonia  (sal  ammoniac). 

Moreover,  if  we  consider  that  the  sulphate  of  am- 
monia may  be  had  for  about  one-fourth  of  the  price  of 
carbonate  of  ammonia,  and  that  in  other  methods  of 
preparing  the  oxide  of  uranium  the  weight  of  car- 
bonate of  ammonia  employed  is  from  three  to  five 
times  that  of  the  sulphate  required  by  the  author's 
process,  the  superiority  of  the  latter  method  is  evident, 
,  besides  possessing  other  advantages. 

"While  engaged  in  the  manufacture  of  uranium 
oxide  by  the  method  thus  described,  the  author  made 
the  following  analysis  to  arrive  at  the  composition  of 
the  urano-sodic  carbonate  which  he  could  not  find 
anywhere. 

a.  30  grains  of  the  compound  gave  7.1  grains  of 
carbonic  acid,  that  is,  23.7  per  cent. 

Z>.  30  grains  were  treated  by  a  solution  of  sal 
ammoniac,  evaporated  to  dryness,  and  then  gently 


416 


MANUFACTURE  OF  COLORS. 


calcined  to  expel  the  excess  of  ammoniacal  salt.  The 
same  treatment  was  repeated  with  a  small  addition  of 
ammonia,  and,  after  washing  and  heating,  the  residue 
was  15.8  grains  of  oxide  of  uranium,  that  is,  52.7  per 
cent. 

c.  The  liquors  and  washings  of  the  previous  test, 
being  evaporated  to  dryness  and  gently  calcined,  left 
a  residue  of  12.9  grains  of  chloride  of  sodium,  corre- 
sponding to  6.7  grains  of  soda,  or  22.9  per  cent. 

Therefore,  the  urano-sodic  carbonate,  precipitated 
in  the  shape  of  a  slightly  soluble  and  lemon-yellow 
colored  powder,  during  the  evaporation  of  the  aqueous 
solutions  of  this  carbonate,  has  the  following  compo- 
sition : — 

Oxide  of  uranium     ....  52.t 

Soda  22.9 

Carbonic  acid  23.7 

Water  0.1 

100.0 

and  its  formula  is  2(mO.CO'0  +  U'O^CO^  which 
composition  corresponds  with  that  of  the  urano- 
potassic  carbonate  analyzed  by  Ebelmen. 

This  compound  is  slowly  dissolved  in  water,  and 
the  saturated  solution,  at  the  temperature  of  about 
15°  O.,  has  a  specific  gravity  of  1.161. 

The  urano-sodic  carbonate  loses  a  little  water  when 
heated  at  a  low  temperature.  By  increasing  the 
temperature,  and  even  below  a  red  heat,  it  loses  the 
greater  part  of  its  carbonic  acid,  and  acquires  a  light 
brick-red  color.  It  will  lose  more  carbonic  acid  at  a 
red  heat,  but  even  by  maintaining  it  at  that  tempera- 
ture for  half  an  hour  it  cannot  be  entirely  deprived  of 
acid. 


YELLOW  COLORS. 


417 


§  24.  Oamhoge, 

Gamboge  is  a  resin  which  oozes  from  the  broken 
branches,  or  from  incisions  made  in  the  trunks  of 
various  trees  which  grow  in  Siam,  Ceylon,  and  Cam- 
bodia. This  substance  is  exported  in  the  shape  of 
cylinders  or  cakes,  which  are  yellowish-brown  at  the 
exterior  and  orange-red  inside,  very  hard,  brittle,  and 
with  a  bright  fracture.  The  powder  is  of  a  deep- 
yellow  color.  This  resin  is  colorless,  slightly  poison- 
ous, and  very  purgative.  Insoluble  in  water,  but 
soluble  in  ether  and  alcohol,  it  is  composed  of  80  per 
cent,  of  pure  resin  and  20  per  cent,  of  gum.  Accord- 
ing to  Mr.  Lefort,  the  yellow  resin  may  be  separated 
from  the  gum  by  solution  in  purified  essence  of  tur- 
pentine. The  greater  part  of  the  essence  may  be 
recovered  by  distillation,  and  the  residue,  being 
evaporated  to  the  consistency  of  an  extract  at  a  low 
temperature,  abandons  a  hyacinth  red  resin  in  lump, 
which  is  of  a  bright-yellow  when  powdered.  It 
mixes  very  well  with  oils. 

Gamboge  is  employed  especially  in  water  and 
miniature  painting.  The  article  purified  in  the  above- 
mentioned  manner  possesses  more  body  than  the  raw 
material,  but  the  price  is  too  high  for  extended  appli- 
cation. 

§  25.  Jaune  Indiea  (^Indian  yellow).  Purree. 

We  now  find  in  the  market  a  coloring  substance, 
which  is  known  in  England  under  the  name  of  purree^ 
and  in  France,  under  that  of  Jaune  Indien  (Indian 
yellow).  The  raw  substance  is  in  the  shape  of  rounded 
lumps,  weighing  from  150  to  200  grammes,  brown- 
green  at  the  exterior,  and  of  a  very  rich  orange-yellow 
27 


418 


MANUFACTURE  OF  COLORS. 


inside.  It  emits  a  smell  similar  to  that  of  castoreiim, 
is  slightly  soluble  in  cold  water,  but  insoluble  in 
alcohol  and  ether.  When  pure,  it  burns  like  tinder, 
and  leaves  a  very  small  residuum.  It  may  be  puri- 
fied by  washing  its  powder  with  boiling  water,  and 
drying  at  a  low  temperature.  Purree  is  a  handsome 
yellow  pigment,  non-poisonous,  and  durable,  but  which 
dries  slowly. 

Indian  yellow  is  still  sold  at  a  high  price,  and  is 
generally  adulterated  with  chrome  yellow  or  other 
yellow  substances.  Mr.  Stenhouse,  from  an  analysis 
made  of  Indian  yellow,  ascertained  that  it  was  a 
combination  of  magnesia  with  a  peculiar  organic 
acid.  This  result  gave  to  Mr.  K.  Wagner  the  idea  of 
preparing  it  artificially,  and  the  following  notice  was 
published  in  the  Technologiste^  vol.  xxi.  page  122: — 

"  There  is  brought  from  the  East  Indies  and  from 
China,  under  the  name  of  purree,  sl  yellow  substance 
which,  from  the  researches  of  MM.  Erdmann  and 
Stenhouse,  consists  principally  of  a  combination  of 
magnesia  with  an  organic  acid,  to  which  the  name  of 
euxanthic  acid  has  been  given.  Pure  purree  or  Indian 
yellow  is  a  handsome  yellow  color,  which  is  often 
preferred  in  oil  painting  to  either  the  chromate  of 
lead  or  of  zinc,  to  the  royal  yellow  (precipitated  sul- 
phide of  arsenic),  and  even  to  the  sulphide  of  cad- 
mium. The  Indian  yellow,  prepared  in  Paris,  does 
not  appear  to  be  obtained  by  purifying  the  raw  mate- 
rial in  boiling  water,  but  by  using  the  pure  euxanthic 
acid.  I  have  also  ascertained  by  the  analysis  of  a 
Parisian  sample,  that  the  inorganic  basis  is  not 
magnesia  alone,  but  magnesia  and  alumina.  A  sam- 
ple, dried  at  100°  C.  and  calcined,  gave  the  following 
results : — 


YELLOW  COLOES. 


419 


Organic  substances  and  water 
Inorganic  residuum 


52.3 
47.7 


100.0 


"  I  have  ascertained  that  the  organic  substance 
is  the  euxanthic  acid,  by  boiling  the  yellow  color  in 
hydrochloric  acid,  in  which  it  is  entirely  soluble.  By 
cooling,  pale-3^ellow  needles  were  deposited,  whicli 
presented  all  the  reactions  of  euxanthic  acid.  Under 
the  action  of  heat  they  melted,  and  produced  a  crys- 
talline sublimate  (euxanthon).  The  calcined  residue 
was  composed  of — 


"This  composition  quite  entirely  agrees  with  that 
of  spinel  (APOlMgO),  and  gives  a  clue  for  the  prepa- 
ration of  euxanthic  yellow. 

"  We  know  from  the  researches  of  Mr.  Habich  that 
when  one  equivalent  of  a  magnesia  salt  is  mixed 
with  an  equivalent  of  an  alumina  salt,  and  when 
sufficient  sal  ammoniac  has  been  added  to  partially 
prevent  the  precipitation  of  the  magnesia,  the  pre-^^ 
cipitate  of  alumina  caused  by  an  addition  of  ammonia, 
will  carry  with  it  enough  magnesia  to  form  an  artifi- 
cial hydrated  spinel.  I  have  also  found  that  the 
aluminous  compound,  equally  with  pure  magnesia,  • 
possesses  the  property  of  forming  with  the  coloring 
sub&tances  a  lake  which  is  remarkable  for  its  porosity. 

"  We  may,  therefore,  obtain  the  euxanthic  yellow 

in  the  following  manner.    We  make  a  solution  of — 

Potassa  alum       .       .       .       .       .45  grammes. 
Sulphate  of  magnesia  ....    13  " 
Sal  ammoniac       .       .       .       .       .      6  " 


Alumina 
Magnesia 


72 
28 


100 


Water 


250 


420 


MANUFACTURE  OF  COLORS. 


"We  dissolve  in  another  vessel  a  few  grammes  of 
euxanthic  acid  in  diluted  ammonia,  and  mix  this  solu- 
tion with  the  previous  one.  The  mixture  is  precipi- 
tated in  the  cold  by  ammonia,  without  any  excess. 
The  yellow  and  bulky  precipitate  thus  formed  is 
washed,  pressed,  and  dried.  This  product,  however, 
is  not  to  be  compared  in  fineness  with  that  manu- 
factured in  Paris,  and  the  preparation  of  which  is 
kept  secret." 

§  26.  Aurwn  mussivum.    Mock  gold.    Mosaic  gold, 
CaVs  gold.    Painter^ s  bronze^  etc. 

This  compound  is  a  bisulphide  of  tin,  which  is 
composed  of — 


It  is  employed  in  oil  painting  for  enhancing  the 
tones  or  the  reflex  of  bronzes,  for  gilding  wood,  etc. 
It  is  formed  of  bright  and  translucent  scales,  soft  to 
the  touch,  odorless  and  tasteless,  and  insoluble  in 
*  water,  alcohol,  ether,  and  oils.  The  following  is  the 
more  generally  employed  process  for  the  manufac- 
ture of  mosaic  gold. 

12  parts  of  tin  are  amalgamated  with  6  parts  of 
mercury,  and  the  amalgam  is  ground  with  7  parts  of 
sublimed  sulphur,  and  6  parts  of  sal  ammoniac.  The 
whole  is  introduced  into  a  strong  glass  matrass, 
which  is  moderately  heated  upon  a  sand-bath  until 
white  fumes  or  sulphuretted  hydrogen  are  no  longer 
produced.  The  temperature  is  then  brought  to  a  red 
heat.  After  cooling,  the  glass  vessel  is  broken,  and 
the  greater  part  of  the  mosaic  gold  is  found  in  the 


Sulphur 


35.3T 
64.63 


Tin 


100.00 


YELLOW  COLORS. 


421 


shape  of  a  scaly  mass,  covered  with  other  crystalline 
and  bright  scales,  which  result  from  the  sublimation 
of  a  part  of  the  compound.  The  more  crystalline 
portions  are  separated,  and  form  a  superior  quality. 

There  are  other  recipes  in  which  the  proportions  of 
tin,  mercury,  and  sulphur  vary.  But  nothing  proves 
that  they  are  better  than  the  preceding  one. 

The  amalgam  of  tin  furnishes  the  finest  article  ;  but 
as  the  mercury  is  generally  lost,  a  more  economical 
process  has  been  sought  for,  which  produces  a  cheaper, 
but  not  so  fine  an  article. 

Out  of  many  formulae,  we  select  the  following  ones: 
Calcine  together 

Sulphur  1  part 

Protoxide  of  tin      .       .       .2  parts 

Or 

Sulphur  3  parts 

Protoxide  of  tin  .  .  .  4  " 
Sal  ammoniac         .       .       .    2  " 

It  results  from  the  researches  of  Mr.  Lefort  that 
all  the  art  in  the  manufacture  of  aurum  mussivum 
rests  on  the  mode  of  conducting  the  fire.  Too  low  a 
temperature  gives  a  light-yellow  product;  more  heat 
results  in  a  deep-yellow  color;  too  much  heat  imparts 
a  grayish  hue. 

§  27.  Nanldn  yellow. 

It  is  said  that  a  fine  nankin  yellow  color  is  obtained 
by  drying,  and  then  calcining,  a  concentrated  solu- 
tion of  nitrate  of  lead,  in  which  has  been  mixed  a 
small  quantity  of  powdered  peat. 

§28.  Chlorophyl 

During  recent  researches  on  the  green  coloring 
matter  of  leaves,  Mr.  Fremy  has  succeeded  in  sepa- 


422 


MANUFACTURE  OF  COLORS. 


rating  it  into  two  principles  :  one,  which  is  blue,  is 
eaWed  phyllocyamn ;  and  the  other,  which  is  yellow, 
bears  the  name  of  j^hylloxantJiin,  These  coloring 
substances,  under  the  influence  of  light,  produce  in- 
soluble combinations,  in  which  it  has  been  possible  to 
vary  the  affinity  of  the  metallic  oxide  for  the  organic 
matter.  The  blue  principle  of  chlorophyl  is  more 
easily  altered  than  the  yellow  one,  and,  under  certain 
circumstances,  it  may  lose  and  reacquire  its  color. 
For  separating  the  two  coloring  principles  which  give 
to  chlorophyl  its  green  coloration,  2  parts  of  ether  are 
shaken  with  1  part  of  slightly  diluted  hydrochloric 
acid,  in  a  glass-stoppered  bottle.  If  the  substance  re- 
sulting from  the  decoloration  of  chlorophyl  be  shaken 
a  few  seconds  with  the  above  liquid,  a  remarkable 
reaction  is  produced :  the  ether  is  rendered  yellow  by 
the  yellow  coloring  principle  which  it  has  retained ; 
the  acid  reacts  upon  the  decolored  portion  of  the 
chlorophyl,  and  reproduces  a  magnificent  blue  sub- 
stance. Under  the  influence  of  bases  the  green  color 
of  leaves  is  transformed  into  a  fine  yellow,  which  is 
soluble  in  alcohol.  It  is  this  transformed  yellow 
which  is  employed  for  the  separation  of  the  constitu- 
ent blue  and  yellow.  This  substance  will  form  an 
insoluble  combination  with  alumina,  that  is,  a  yellow 
lake  which  will  deliver  its  color  to  neutral  solvents, 
such  as  alcohol,  ether,  and  bisulphide  of  carbon.  We 
believe  that  the  day  will  come  when  the  arts  will 
utilize  the  green  and  yellow  lakes,  which  are  so  easily 
prepared  with  chlorophyl. 


EED  COLORS. 


423 


SECTION  IV. 

RED  COLORS. 

§  1.  Red  ocJire. 

"When  considering  the  yellow  ochres  we  indicated 
the  mode  of  manufacture  of  red  ochres,  and  we 
added  that  the  oxide  of  iron  which  forms  their  basis 
acquires  the  most  varied  tones  and  hues  under  the 
influence  of  heat.  The  sesquioxide  of  iron  obtained 
by  the  calcination  in  a  mufiie,  and  with  the  access  of 
the  air,  of  the  sulphate  of  protoxide  of  iron,  is  either 
orange-red,  blood-red,  flesh-red,  or  carmine-red,  ac- 
cordingly as  the  heat  has  been  more  and  more  in- 
creased. A  white  heat  will  give  it  a  violet  tinge,  and 
artists  use  this  article  under  the  name  of  violet  from 
iron.  Some  others  are  reddish-brown,  others  are 
grayish.  The  same  principle  applies  to  the  manu- 
facture of  the  red  colors  employed  for  painting  on 
porcelain  and  glass. 

Analogous  colors  have  been  i;ged  for  a  long  time  in 
oil  painting,  and  MM.  Bourgeois  and  Colomb-Bour- 
geois,  Ferrand-Dosnon,  and  others,  have  successfully 
manufactured  certain  reds,  called  Mars  reds,  browns, 
and  violets,  which  were  carefully  prepared  from  pure 
copperas. 

These  changes  in  the  coloration  of  the  oxide  of  iron 
are  reproduced  in  the  majority  of  substances  which 
contain  it,  especially  the  earths.  Moreover,  when, 
besides  the  iron  oxide,  there  are  other  oxides,  calcina- 
tion will  produce  different  hues  which  may  be  as  use- 
ful as  the  reds  and  browns  we  have  mentioned.  Thus, 
water,  which  forms  with  the  oxide  of  iron  a  hydrated 
combination  of  a  pale-yellow  color,  will  be  replaced 


424 


MAJ^UFACTURE  OF  COLORS. 


by  zinc  oxide  if  the  two  oxides  are  calcined  together, 
and  the  resulting  compound  will  have  a  fast  and 
durable  color.  Alumina  produces  an  orange  alumi- 
nate.  The  oxides  of  manganese,  cobalt,  nickel, 
copper,  etc., -form  with  the  oxides  of  iron  certain 
browns  possessing  a  depth  of  coloration  in  a  ratio 
with  their  proportion  in  the  compound. 

§  2.  ColcotJiar,    English  red  or  rouge. 

This  is  a  red  sesqui oxide  of  iron,  which  forms  a  very 
durable  and  bright  color,  and  is  obtained  by  the  cal- 
cination of  the  green  sulphate  of  iron  (copperas)  upon 
iron  plates,  until  it  has  lost  all  its  combined  water 
and  has  become  white.  It  is  then  pulverized,  placed 
in  stoneware  pots,  and  submitted  to  a  red  heat.  Dur- 
ing the  operation,  sulphurous  acid  and  glacial  (Nord- 
hausen)  sulphuric  acid  distil  over,  and  the  residue 
of  the  retort  is  a  hard  mass  which  is  coarsely  pow- 
dered, washed,  dried,  finely  ground,  and  sifted.  The 
finer  qualities  are  obtained  by  levigation  (floating). 
The  latter,  after  drying,  are  sometimes  calcined  anew, 
in  order  to  increase  their  brightness. 

Colcothar  is  also  produced  by  the  wet  way,  in  mix- 
ing a  solution  of  sulphate  of  iron  with  another  of  car- 
bonate or,  better  still,  bicarbonate  of  soda.  There  is 
formed  a  soluble  sulphate  of  soda,  and  a  precipitate  of 
carbonate  of  protoxide  of  iron,  which  is  soon  trans- 
formed into  hydrated  sesquioxide  of  iron.  This  is 
washed,  dried,  and  calcined  at  a  red  heat  in  clay  cru- 
cibles. 

It  is  said  that,  when  the  precipitation  is  effected  in 
hot  liquors,  the  colcothar  is  finer,  more  velvety,  and 
deeper  in  color. 

It  may  be  mixed  with  other  iron  colors,  or  calcined 
with  lampblack,  for  obtaining  various  tones  of  color. 


RED  COLORS. 


425 


In  the  latter  case,  there  is  a  partial  reduction  of  the 
red  oxide  of  iron  to  the  black  magnetic  state. 

§  3.  Armenian  hole,    Ochreous  clay.    Lemnos  earth. 
Oriental  hole.    Red  hole. 

These  various  names  apply  to  a  yellowish-red  pig- 
ment, which  was  formerly  imported  from  the  East, 
but  which  is  now  prepared  from  certain  earths  found 
at  Meudon,  in  Burgundy^  near  Saumur,  Blois,  etc., 
and  which  contain  clay,  oxide  of  iron,  silica,  lime,  and 
magnesia. 

The  finest  pieces  are  picked  up,  and  softened  in 
water,  then  lixiviated  for  separating  the  coarse  and 
hard  particles.  The  finer  portions  are  allowed  to 
settle,  and  the  deposited  paste  is  dried  in  the  sun,  or 
moulded  into  troches  or  balls.  This  color  is  durable, 
but  the  red  is  somewhat  yellowish. 

§  4.  Iron  minium. 

The  iron  minium  is  a  red  color,  prepared  in  Bel- 
gium by  Mr.  de  Cartret.  It  is  a  mixture  of  clay  and 
oxide  of  iron  which  is  in  the  shape  of  a  fine  powder 
having  a  deep  red-brown  color.    Its  composition  is — 


Hygroscopic  water   2.75 

Oxide  of  iron       .       .   68.iit 

Clay   27.60 

Alumina   0.27 

Lime   0.40 


99.29 

An  iron  minium  prepared  in  Holland  w^as  found 
by  Mr.  Bleekrode  to  be  composed  of — 

Water  6.00 

Oxide  of  iron  85.57 

Clay  8.43 


100.00 


426 


MANUFACTURE  OF  COLORS. 


The  difference  between  the  iron  minium  and  the  red 
ochre  consists,  therefore,  in  the  proportion  of  peroxide 
of  iron.  In  ochres,  the  proportion  of  oxide  is  not  over 
39  per  cent.,  and  generally  is  much  less.  Colcothar  or 
English  rouge  contains  sometimes  not  more  than  40 
per  cent,  of  oxide,  the  remainder  being  sulphate  of 
lime.  The  Berlin  hrown-red  is  prepared  with  the 
iron  residue  of  the  manufacture  of  alum,  and  alwaj^s 
contains  free  sulphuric  acid. 

The  iron  minium  is,  according  to  Mr.  Wagner, 
more  economical  than  that  of  lead,  in  the  ratio  of  20 
to  39. 

§  5.  JRed-brown, 

Eed-brown  is  quite  a  handsome  reddish  substance, 
very  durable,  but  little  used.  It  is  obtained  by  fusing 
in  a  clay  crucible,  1  part  of  red  oxide  of  iron  and 
10  parts  of  litharge  or  red  lead,  which  have  been 
thoroughly  mixed.  After  cooling,  the  mixture  is 
ground. 

§  6.  Red  lead  or  minium. 

Eed  lead  or  minium  is  a  very  bright  orange-red 
powder,  composed,  says  Mr.  Dumas,  of  two  parts  of 
protoxide,  and  one  part  of  binoxide  of  lead.  It  is  pre- 
pared by  pulverizing  massicot  (yellow  litharge),  and 
submitting  it  to  a  red  heat  in  a  reverberatory  furnace, 
where  a  portion  of  the  protoxide  passes  to  the  state 
of  binoxide.  If  the  product  be  heated  two  or  three 
different  times,  it  bears  the  names  of  two  fires  or  three 
fires  red  lead,  and  is  of  a  very  rich  red  color. 

Red  lead  is  also  manufactured  by  decomposing  at 
a  high  temperature  white  lead  or  carbonate  of  lead. 
This  salt  loses  its  carbonic  acid,  and  leaves  a  re- 
siduum of  red  lead.    We  shall  now  describe  the 


EED  COLORS. 


427 


manner  in  which  this  pigment  is  manufactured  at 
Portillon,  near  Tours. 

We  have  ah-eady  seen  (white  colors)  that  the  oxide 
of  lead  produced  at  the  works  of  Portillon  is  sepa- 
rated into  two  parts  :  one  for  the  manufacture  of  white 
lead,  the  other  for  that  of  red  lead. 

The  crude  oxide  is  powdered  and  separated  from 
the  still  remaining  metal  (blue  lead)  in  a  small  mill. 
This  apparatus  is  composed  of  a  horizontal  and  cir- 
cular cast-iron  plate  upon  which  rolls  a  cast-iron 
mill-stone.  Below  the  plate  and  between  the  cast- 
iron  bottom  of  the  tub  which  incloses  the  whole, 
there  is  the  stirring  apparatus  proper. 

The  mode  of  working  is  as  follows :  The  crude  oxide 
is  put  into  the  mill  and  ground  under  the  stone  ;  the 
stirring  apparatus  keeps  the  light  particles  in  suspen- 
sion in  water,  and  they  are  carried  with  it,  through 
the  overflow  of  the  tub,  into  the  various  settling  tanks 
below.  The  heavy  unoxidized  lead  remains  at  the 
bottom  of  the  mill  tub,  and  is  now  and  then  removed 
by  a  trap  door,  to  be  oxidized  again  in  the  furnaces. 
The  circulation  of  water  between  the  head  and  tail  of 
the  complete  apparatus  is  kept  up  by  a  chain  and 
buckets.  There  are  three  such  mills  at  work,  one 
being  especially  intended  for  the  grinding  of  the 
purest  oxides  for  the  red  lead  used  by  flint  glass- 
works. 

When  the  settling  tanks  have  received  a  sufficient 
quantity  of  oxide  the  latter  is  made  to  flow  into  a 
basin  near  the  furnaces,  where  it  loses  the  greater 
proportion  of  its  water. 

The  drained  oxide  is  then  placed  in  rectangular 
sheet-iron  trays,  capable  of  holding  15  kilogrammes 
of  litharge  (massicot)  each.    100  filled  trays  make  a 


428 


MAXUFACTURE  OF  COLORS. 


charge,  and  are  put  into  the  hot  furnaces  at  the  end 
of  each  day.  All  the  openings  are  closed,  especially 
that  of  the  chimney,  which  is  shut  with  a  well-fitting 
damper.  The  same  trays  are  submitted  three  or  four 
times  to  the  same  treatment,  after  which  the  oxide  or 
massicot  has  become  red  lead.  This  substance  is  in 
the  shape  of  more  or  less  coarse  lumps,  the  color  of 
which  is  not  the  same  in  all  the  trays;  but  the  mixing 
of  the  whole  insures  a  certain  regularity  of  coloration. 

The  red  lead  is  then  powdered  in  a  ventilator,  the 
blades  of  which  break  the  pieces.  The  light  por- 
tions are  carried,  by  the  draft  of  air,  up  a  sheet-iron 
pipe  12  metres  high,  and  are  collected  in  a  sheet-iron 
reservoir.  This  mode  of  powdering  is  interesting, 
and  its  employment  should  be  more  extended.  The 
red  lead  is  prevented  from  falling  upon  the  blades  of 
the  ventilator,  except  in  small  quantities  at  a  time, 
by  means  of  a  distributing  apparatus  composed  of  a 
grooved  cast-iron  cylinder,  wdiich  turns  slowly.  The 
grooves  receive  the  red  lead.  The  salubiity  of  the 
apparatus  is  still  further  increased  by  a  special  fan, 
which  exhausts  the  air  on  top  of  the  box  into  which 
the  red  lead  to  be  ground  is  poured.  The  workman 
is  therefore  in  the  middle  of  a  draught  which  carries 
all  of  the  dust  from  him.  The  air,  exhausted  by  the 
fan,  passes  through  long  wooden  boxes,  where  it 
leaves  the  greater  part  of  the  dust,  and  is  then  carried 
out  into  the  atmosphere  by  means  of  a  high  stack. 

§  7.  Orange  mineral. 

Orange  mineral,  according  to  Mulder,  is  a  definite 
combination  of  protoxide  and  binoxide  of  lead,  in 
which  there  remains  a  small  proportion  of  undecom- 
posed  white  lead.    This  chemist  believes  that  the 


RED  COLORS. 


429 


following  analysis  gives  the  correct  composition  of 
orange  mineral : — 

Protoxide  of  lead      .       .  .       .  . 

Binoxide  of  lead        ......  25 

Carbonic  acid  2 

100 

The  greater  the  proportion  of  binoxide  of  lead,  the 
deeper  is  the  red  hue  of  orange  mineral. 

The  following  is  the  mode  pursued  in  the  manu- 
facture of  this  pigment  at  the  works  of  Port il Ion, 
near  Tours. 

We  know  that  orange  mineral  results  from  the  cal- 
cination of  white  lead.  This  sttbstance  is  coarsely 
broken  and  put  into  sheet-iron  trays  similar  to  those 
employed  for  red  lead,  and  with  which  the  oxidizing 
furnaces,  hot  from  the  day's  work,  are  charged.  When 
the  action  of  the  heat  is  completed,  the  orange  min- 
eral is  removed  from  the  fire,  cooled,  and  then  thrown 
into  the  distributing  apparatus  of  a  grinding  venti- 
lator, which  is  similar  to  that  used  for  red  lead.  The 
powdered  orange  mineral  falls  upon  a  horizontal 
metallic  sieve,  and  the  draft  created  by  a  special  fan 
prevents  any  dust  from  flying  about  the  rooms. 

§  8.  Realgai^  or  ruhy  of  arsenic. 

Realgar  is  a  yellow-red  bisulphide  of  arsenic,  which 
is  found  native  in  certain  of  the  old  rocks,  but  which 
is  more  generally  prepared  by  melting  in  a  crucible 
a  mixture  of  8  parts  of  arsenious  acid  and  4  parts  of 
stiblimed  sulphur.  The  hard,  brittle,  and  opaque  sub- 
stance remainino^  in  the  crucible  after  cooling*,  is 
powdered.  This  poisonous  pigment  is  not  very  dura- 
ble, and  should  not  be  mixed  with  lead  or  mercury 
colors,  which  are  decomposed  by  it. 


430 


MANUFACTURE  OF  COLORS. 


§  9.  Cinncibar  and  vermilion. 

We  find  in  the  natural  state,  and  we  manufacture 
artificially,  a  fine  blood-red  color,  wliich  is  called 
cimiahar,  when  crystalline,  and  vermilion,  when  pow- 
dered. This  red  sulphide  of  mercury  is  found  in  all 
mercury  mines. 

1.  Manufacture  by  the  Dry  Way. 

Cinnabar  is  prepared  at  the  mercury  mines  of  Idria, 
by  grinding  finely  in  revolving  tuns,  85  parts  of  mer- 
cury and  15  of  sulphur.  The  mixture  is  then  heated 
in  cast-iron  cylinders,  and  sublimed  in  condensers 
made  of  clay.  The  vermilion  is  obtained  by  grind- 
ing the  cinnabar  in  water. 

Mr.  Ritter  assures  us  that  the  renowned  Holland 
vermilion  is  prepared  by  grinding  thoroughly  a  mix- 
ture of  1  part  of  sulphur  and  2  of  mercury,  and  by 
adding  to  100  parts  of  the  mixture  2.5  parts  of  granu- 
lated lead  or  red  lead.  Each  sublimation  pot  receives 
about  100  kilogrammes  of  mixture,  which  is  heated 
as  shall  be  explained  further  on.  After  eighteen  or 
twenty  hours  of  cooling,  the  pots  are  broken,  and 
their  contents  ground  in  a  mill.  The  lead,  in  the 
state  of  sulphide,  remains  at  the  bottom  of  the  vessels. 

Mr.  Tuckert  has  also  indicated  the  following  differ- 
ent mode  of  preparation,  which  is  pursued  success- 
fully in  Holland : — 

An  intimate  mixture  is  made  of  75  kilogrammes 
of  sublimed  sulphur  (sifted)  and  540  kilogrammes  of 
mercury  (passed  through  a  chamois  skin).  The 
whole  is  moderately  heated  upon  a  shallow  iron  pan, 
and  the  resulting  ethiops  (black  sulphide)  is  coarsely 
broken,  then  ground  and  kept  in  jars.    Its  transfor- 


RED  COLOKS. 


431 


mation  into  cinnabar  is  effected  in  large  clay  pots, 
well  luted,  and  brought  to  a  dark-red  heat  in  isolated 
furnaces.  The  operation  begins  with  the  contents  of 
two  or  three  jars  of  ethiops.  The  substance  becomes 
inflamed,  and  as  soon  as  the  flame  diminishes  in 
intensity  the  pots  are  covered  with  a  well-fitting 
thick  iron  plate.  The  fire  is  kept  up  for  thirty-six 
hours,  and  is  so  regulated  that  the  flame  produced 
by  removing  the  iron  cover  will  rise  to  about  10  or  12 
centimetres  above  the  opening  of  the  pot.  The  sub- 
limation is  aided  by  stirring  the  mass  every  half  hour 
with  an  iron  rod.  'New  additions  of  ethiops  are  made 
every  four  or  five  hours.  The  cinnabar  is  deposited 
upon  the  inward  surfaces  of  the  apparatus.  After 
cooling,  the  pots  are  broken,  and  the  pigment  is 
finely  ground  in  a  mill.  The  powder  is  afterwards 
levigated  in  order  to  arrive  at  a  greater  degree  of 
comminution,  for  the  finer  the  vermilion  the  greater 
are  its  fire  and  brightness. 

It  is  recommended  for  this  manufacture  to  operate 
on  a  large  scale  with  pure  materials,  to  heat  at  the 
proper  point,  and  to  volatilize  all  the  sulphur  which 
is. not  combined. 

2.  Manufacture  by  the  Wet  Way. 

"Vermilion  may  also  be  obtained  by  the  wet  way 
in  a  state  of  impalpable  powder.  This  is  the  method 
employed  by  the  Chinese  in  preparing,  by  scarcely 
known  processes,  the  so-called  Chinese  vermilion, 
which  is  one  of  the  finest  and  the  most  souo-ht  for  in 
the  trade.  All  the  processes  proposed  in  Europe  up 
to  the  present  time  are* based  upon  the  employment  of 
a  caustic  alkali,  generally  potassa.  "We  shall  rapidly 
describe  four  processes :  one  by  Mr.  Kirchoff,  of  St. 


432 


MANUFACTURE  OF  COLORS. 


Petersburg;  another  by  Mr.  Brnnner,  of  Berne;  the 
third  by  Mr.  Jaequelin,  of  Paris;  and  the  fourth  by 
Mr.  Firmenich,  of  Cologne. 

A.  Kir  chaff  Proceiis, 

This  process  is  somewhat  difficult  of  operation. 
300  parts  of  mercury  are  ground  in  a  mortar  with  68 
parts  of  sublimed  sulphur,  which  has  been  moistened 
with  a  few  drops  of  caustic  potassa.  The  ethiops,  or 
black  sulphide  of  mercury  thus  formed,  is  mixed  with 
160  parts  of  caustic  potassa  dissolved  in  a  very  small 
volume  of  water.  The  whole  is  heated  upon  a  sand- 
bath  for  a  half  hour,  and  water  is  added  to  make  up  for 
that  evaporated.  After  that  time  no  more  water  is 
introduced,  and  the  substance  which  is  kept  stirred 
becomes  brown  and  gelatinous,  and  then  red.  When 
all  of  the  mixture  has  turned  a  fine  red  color,  it  is 
carried  to  the  stove-room,  and  is  there  now  and  then 
stirred.  Lastly,  the  vermilion  is  washed  several 
times,  drained,  and  dried  at  a  low  temperature. 
Sometimes  it  is  digested  in  caustic  potassa. 

B.  Brunner  Process. 

Take  300  grammes  of  mercury,  114  of  sulphur,  75 
of  hydrated  potassa,  and  450  grammes  of  water. 
Thoroughly  mix  and  grind  the  mercury  and  sulphur, 
then  pour  upon  the  ethiops  thus  formed,  by  small  por- 
tions at  a  time,  the  solution  of  potassa,  and  stir  it.  Put 
the  mixture  into  vessels  of  porcelain,  earthenware,  or 
cast-iron,  and  heat  on  a  sand-bath  at  a  temperature 
of  from  45°  to  50°  C.  After  7  or  8  hours  of  such 
heating,  during  which  the  evaporated  water  has  been 
replaced,  the  product  passes  from  a  black  to  a  brown- 
red,  and  lastly  to  a  scarlet-red.    When  the  vermilion 


RED  COLOKS. 


433 


has  acquired  its  greatest  degree  of  brightness,  it  is 
removed  from  the  fire,  then  digested  for  some  time  at 
a  low  temperature,  and  lastly  washed  several  times, 
and  separated  from  the  uncombined  mercury. 

C.  Jacquelin  Process. 

The  proportions  of  the  raw  materials  are  different  in 
this  case.  Take  90  grammes  of  mercury,  30  of  sul- 
phur, 20  of  hydrated  potassa,  and  30  grammes  of 
water.  The  mercury  and  the  sulphur  are  placed  in  a 
shallow  cast-iron  dish,  dipping  into  cold  water,  and 
the  solution  of  potassa  is  added  by  degrees  w^iile  the 
substances  are  stirred  with  a  large  pestle.  When  all 
the  potassa  has  been  added,  the  dish  is  heated  at 
80°  C.  for  one  hour,  and  the  evaporated  water  is  re- 
placed. After  that,  the  vermilion  is  washed  in  five 
or  six  times  its  weight  of  boiling  water,  and  the  still 
hot  liquor  is  decanted  with  the  uncombined  and  sus- 
pended sulphur.  Other  washings  with  cold  water 
remove  the  alkaline  sulphides.  Lastly,  the  vermilion 
is  collected  upon  a  filter,  drained,  and  dried. 

We  see  that  there  is  a  great  analogy  between  all  of 
these  processes,  and  that,  to  arrive  at  a  fine  quality  of 
vermilion,  the  success  appears  to  depend  upon  pure 
materials,  good  proportions,  and,  especially,  a  proper 
temperature.  Indeed,  we  know  that  vermilion  loses 
part  of  its  brightness  when  it  has  been  overheated. 

Mr.  Weshle  assures  us  that  he  can  produce  a  bright 
vermilion  by  finely  pulverizing  cinnabar,  mixing  it 
with  1  per  cent,  of  sulphide  of  antimony,  and  boiling 
it  several  times  with  3  parts  of  sulphide  of  potassium 
in  a  cast-iron  pot.  The  precipitate  is  then  washed 
with  pure  water,  digested  with  hydrochloric  acid,  and 
washed  again.  There  is  nothing  surprising  in  this 
28 


434 


MAKUFACTURE  OF  COLORS. 


process,  since  we  know  that  under  certain  circum- 
stances the  sulphide  of  antimony  acquires  a  fine  red 
color,  as  we  shall  see  further  on. 

D.  Firmenich  Process. 

Cinnabar,  says  Mr.  Firmenich,  is  found  in  the 
native  state,  either  in  crystals,  or  compact  and  earthy 
crystalline,  or  fibrous,  or  pulverulent,  etc.  It  is  found 
in  pockets  or  in  veins,  or  is  earthy  and  mixed  with 
other  rocks.  It  is  chemically  prepared  either  by  the 
dry  or  by  the  wet  way. 

In  the  manufacture  of  cinnabar,  7  parts  of  mercury 
and  1  of  sulphur  are  melted  in  an  iron  vessel,  and  the 
resulting  sulphide  is  then  sublimed  in  other  vases  of 
refractory  clay.  At  Idria,  the  first  mixture  is  efiected 
in  rotary  tuns,  and  the  chemical  combination  and  the 
sublimation  take  place  in  heated  cast-iron  retorts. 

A  process  which  is  less  known,  and  which  gives 
better  results  than  all  of  the  other  methods,  in  the 
beauty  of  the  color  and  the  resistance  to  the  fire,  is 
that  with  the  sulphide  of  potassium.  This  mode  of 
operation  supposes  this  reagent  to  be  in  a  great  state 
of  purity.  There  are  various  methods  of  preparing  it, 
but  we  should  discard  those  by  which  a  lye  of  caustic 
potassa  is  boiled  with  an  excess  of  sublimed  sulphur, 
or  when  potassa  and  sulphur  are  fused  together,  be- 
cause there  is  also  formed  a  hyposulphite  or  a  sulphate 
of  potassa,  which  comes  in  the  way  of  the  prepara- 
tion of  the  cinnabar. 

A  pure  sulphide  of  potassium  is  obtained  by  re- 
ducing the  sulphate  of  potassa^  with  charcoal,  and 

*  The  author  employs  and  repeats  the  words  "  sulphide  of 
potassa,"  which  we  do  not  understand,  and  for  which  we  have 
substituted  those  of  "  sulphate  of  potassa." — Trans. 


RED  COLORS. 


435 


saturating  the  lye  afterwards  with  sulphur  to  the 
degree  required  for  the  operation. 

For  instance,  20  parts  of  sulphate  of  potassa^  and 
6  of  charcoal  are  finely  powdered,  and  thoroughly 
mixed.  The  whole  is  then  strongly  heated  in  a 
Hessian  crucible,  luted  and  placed  in  an  air  furnace. 
Although  not  seen,  the  mixture  boils  in  a  lively  way, 
and  the  crucible  should  not  be  filled  to  more  than 
two-thirds  of  its  capacity.  The  melted  and  cooled 
mass  is  a  simple  sulphide  of  potassium  (KS),  which 
presents  a  crystalline  appearance,  is  colored  brown  or 
red,  and  attracts  the  dampness  of  the  air.  It  is  boiled 
in  a  cast-iron  kettle  with  pure  or  rain  water,  in  the 
ratio  of  2  parts  of  substance  to  7  of  water,  and  is 
then  filtered.  By  cooling,  the  undecomposed  sul- 
phate of  potassa^  crystallizes  on  the  sides  of  the 
vessel. 

Thus  purified,  the  lye  is  again  boiled  with  pow- 
dered sulphur,  which  is  added  by  small  quantities  at 
a  time,  until  saturation,  which  is  ascertained  by  the 
efiervescence  of  the  liquor,  and  the  formation  of  bub- 
bles at  its  surface.  The  simple  sulphide  of  potassium, 
by  this  saturation,  absorbs  4  atoms  of  sulphur.  The 
contact  of  the  air  should  be  avoided  as  far  as  practi- 
cable, because  its  oxygen  decomposes  the  sulphide. 

The  cinnabar  is  manufactured  as  follows :  Bottles 
are  filled  with  5  kilogrammes  of  mercury,  1  of  sul- 
phur, and  2.25  of  the  lye  of  sulphide  of  potassium, 
and,  after  having  been  moderately  heated,  they  are 
shaken,  two  at  a  time,  in  a  basket  hanging  from  a 
spring,  and  striking  a  straw  mattress  in  its  descent. 

*  The  author  employs  and  repeats  the  words  "sulphide  of 
potassa,"  which  we  do  not  understand,  and  for  which  we  have 
substituted  those  of  "  sulphate  of  potassa." — Trans. 


436 


MANUFACTURE  OF  COLORS. 


After  one  and  a  half  or  two  hours  of  such  motion, 
the  bottles  become  hot,  and  the  mixture  acquires  a 
greenish-brown  color.  The  mercury  combines  with 
the  sulphur  of  the  lye,  while  the  latter  keeps  up  its 
degree  of  saturation  from  the  added  sulphur. 

In  order  to  keep  the  mixture  in  a  greater  state  of 
division  and  more  porous,  it  is  recommended  now  and 
then  to  turn  the  bottles.  After  three  and  a  half  hours 
the  mercury  is  entirely  combined,  and  the  mixture  is 
a  dark-brown.  It  is  then  left  to  cool  off  slowly.  The 
whole  operation  lasts  five  hours.  The  bottles  are 
next  carried  into  a  stove-room,  where  the  temperature 
is  maintained  at  from  45°  to  50°  C,  and  where  the 
mixture  gradually  turns  red.  This  heating  continues 
from  two  to  three  days,  and  the  contents  of  the  bottles 
should  be  well  stirred  three  or  four  times  every  day. 

The  temperature  has  a  decisive  action  upon  the 
tone  of  the  color;  the  cooler  the  mixture  before  the 
shaking  operation,  the  lighter  will  be  the  color  of  the 
product.  For  instance,  a  light  carmine  cinnabar  with 
a  yellowish  tinge  is  prepared  by  cooling  the  bottles 
for  one  hour  in  the  open  air,  in  winter ;  but  in  sum- 
mer they  are  cooled  in  water. 

It  now  remains  to  free  the  cinnabar  from  the  excess 
of  sulphur,  and  this  is  done  in  the  following  manner: 
About  6  decilitres  of  pure  water  are  added  to  each 
bottle,  which  is  shaken  and  emptied  upon  a  filter. 
The  clear  lye  runs  out,  and  the  remaining  cinnabar  is 
put  into  a  stoneware  pot,  where  it  is  mixed  with  a  lye 
of  caustic  soda,  which  dissolves  the  remaining  free 
sulphur.  Some  time  afterwards  the  lye  is  decanted 
as  completely  as  possible,  and  the  deposit  is  washed 
several  times  by  decantation,  and  lastly,  upon  a  filter. 

The  solution  of  the  excess  of  sulphur,  and  the 


RED  COLORS. 


437 


washing  off  of  the  caustic  lye,  require  a  great  deal  of 
care.  Indeed,  the  resistance  of  the  product  to  the 
action  of  the  fire  entirely  depends  upon  the  first 
operation;  the  second  insures  the  greater  or  less 
durability  of  the  color.  The  filtration  takes  from  two 
to  three  days,  and  the  drying  is  efiected  at  a  very 
low  temperature  until  the  cinnabar  can  be  broken  to 
pieces,  and  is  dry  to  the  touch.  It  is  then  placed  in 
iron  basins,  and  is  repeatedly  stirred,  while  the  tem- 
perature of  the  stove-room  is  raised  to  60°  or  62°  C. 

Undei-  the  influence  of  too  much  heat  the  cinnabar 
becomes  of  a  darker  color;  this  is  not  a  defect,  since 
the  color  becomes  more  steady  when  exposed  to  the 
fire.    This  last  drying  requires  about  five  hours. 

As  we  have  already  stated,  this  mode  of  preparing 
cinnabar  is  to  be  preferred  to  all  others,  because  the 
product  answers  the  requirements  of  beauty  of  color, 
and  is  capable  of  withstanding  fire,  the  latter  quality 
especially  being  wanting  in  most  of  the  other  cinna- 
bars. Moreover,  the  figures  prove  that  this  method 
produces  a  cheaper  cinnabar  than  those  prepared  in 
the  usual  manner. 

Many  trials  have  been  made  to  brighten  the  color 
of  vermilion  and  increase  its  fire.  Here  are  some 
results : — 

Desmoulins,  in  1825,  employed  a  lye  of  caustic 
potassa.  Mr.  Dumas,  in  his  Traite  de  Cliimie^  states 
that  unsuccessful  attempts  have  been  made  with  nitric 
acid  to  impart  to  French  vermilion  the  brightness  of 
that  of  China.  However,  the  particulars  as  to  the 
proportion  and  strength  of  the  acid  were  not  made 
public.  MM.  Pelouze  &  Fremy,  in  their  Cours  de 
Chimie^  indicate  the  use  of  hydrochloric  acid  for 
washing  the  paste  of  vermilion. 


438 


MAlSrUFACTURE  OF  COLORS. 


Lastly,  it  appears  from  a  recent  lawsuit  that  Mr. 
Ringault,  Sr.,  manufacturer  of  colors  at  Paris,  took 
out,  on  the  15th  of  October,  1859,  a  patent  for  the 
preparation  of  a  vermilion  unalterable  by  fire.  The 
process  consists  in  a  method  of  purifying  and 
brightening  the  cinnabar  ground  in  water,  so  that 
the  resulting  vermilion  acquires  a  depth  of  color  and 
a  durability  seldom  arrived  at.  Here  are  the  various 
operations : — 

1.  Treatment  with  nitric  acid,  which  removes  all 
the  excess  of  sulphur. 

2.  Treatment  by  a  hot  mixture  of  sulphide  of  potas- 
sium and  caustic  potassa. 

3.  Digestion  of  the  vermilion  in  hydrochloric  acid. 

4.  Hot  treatment  of  the  paste  with  a  solution  of 
caustic  potassa,  in  order  to  give  a  more  or  less  violet 
tinge  to  the  vermilion. 

Mr.  Desmottes,  manufacturer  of  vermilion  at  Paris, 
has  tried  to  imitate  this  process  as  follows :  The 
vermilion  is  treated  by  nitric  acid,  with  the  useless 
addition  of  acetic  acid.  Then  comes  the  employment 
of  a  hot  solution  of  potassa,  to  which  powdered  sul- 
phur is  added.  Lastly,  the  paste  is  digested  with 
hydrochloric  acid.  The  process  is  the  same  as  that, 
of  Eingault,  and  produces  vermilions  possessing  the 
desired  qualities  of  brightness  and  durability. 

Vermilion  is  quite  often  adulterated.  Its  purity 
may  be  ascertained  by  heating  it  in  a  closed  vessel. 
The  pure  article  is  entirely  volatilized,  whereas  the 
impurities,  such  as  powdered  brick,  red  lead,  red 
ochre,  colcothar,  etc.,  remain  on  the  bottom  of  the 
vessel.  By  a  treatment  with  hot  nitric  acid  a  ver- 
milion holding  red  lead  or  orange  mineral  becomes 


RED  COLORS. 


439 


brown.  Thrown  upon  burning  coals  it  emits  garlic- 
smelling  fumes  if  it  has  been  adulterated  with  realgar. 

It  is  useless  to  say  that  cinnabar  and  vermilion  are 
poisonous  colors. 

§  10.  Iodide  of  mercury. 

The  iodide,  or  rather  the  bi-iodide  of  mercury,  is  a 
salt  possessing  a  red  color  of  the  greatest  brightness, 
but  which  is  rendered  yellow,  and  then  black,  by  the 
action  of  light.  It  is  scarcely  employed  now-a-days, 
except  in  water  colors.  Moreover,  it  is  highly  poison- 
ous, and  there  are  several  other  pigments,  which  when 
mixed  with  it,  decompose  it. 

The  preparation  of  this  oxide,  which  is  called 
scarlet  in  England,  is  quite  easy.  Two  dilute  solu- 
tions, one  of  80  parts  of  bichloride  of  mercury  (corro- 
sive sublimate)  and  the  other  of  100  parts  of  iodide 
of  potassium,  are  mixed  together,  and  the  resulting 
precipitate  is  washed  with  distilled  water,  first  in  the 
vessel  and  then  upon  a  filter,  and  lastly,  dried  at  a 
low  temperature.  This  color  should  be  kept  in  black 
bottles. 

Heller  affirms  that  this  bi-iodide  becomes  more 
durable  if  it  be  dissolved  in  a  hot  and  concentrated 
solution  of  sal  ammoniac.  By  cooling,  the  color  is 
precipitated  in  the  shape  of  fine  purple  crystals,  which 
are  washed  and  finely  pulverized. 

§  11.  Chromates  of  mercury. 

The  combination  of  chromic  acid  with  the  binoxide 
of  mercury  furnishes,  according  to  Mr.  Millon,  two 
chromates  which  differ  in  their  composition  and  their 
color. 

The  first  of  these  chromates  is  obtained  by  pouring 


440 


MANUFACTURE  OF  COLORS. 


a  solution  of  chromate  of  potassa  into  a  solution  of 
nitrate  of  binoxide  of  mercury.  A  very  dark  brick- 
red  precipitate  is  formed,  which  is  washed  several 
times  by  decantation,  and  then  dried  in  the  air  and  in 
the  dark. 

The  other  chromate  is  prepared  by  boiling  for  a 
long  time,  the  red  oxide  of  mercury  with  a  concen- 
trated solution  of  bichromate  of  potassa.  The  pre- 
cipitate is  separated  by  decantation,  washed  several 
times  with  hot  water,  and  dried  in  a  dark  place. 
"When  it  has  been  well  prepared  it  has  a  fine  violet 
tinge. 

These  colors  are  costly  of  production,  and  are 
easily  decomposed  by  light. 

§  12.  Chromate  of  copper.  Maroon-red, 

This  color  is  not  yet  very  well  known,  and  is  pre- 
pared with  a  boiling  solution  of  sulphate  of  copper, 
poured,  drop  by  drop,  into  another  boiling  solution  of 
neutral  chromate  of  potassa.  There  are  formed  a  solu- 
ble sulphate  of  potassa  and  a  precipitate  of  chromate 
of  copper,  which  are  washed  by  decantation  with  hot 
water  until  the  latter  is  colorless.  It  is  afterwards 
collected  and  drained  upon  a  filter  and  dried  in  a 
stove. 

§  13.  Chromate  of  silvei\  Purple-red, 

The  chromate  of  silver  is  a  color  without  much 
durability,  which  is  employed  only  in  miniature  paint- 
ing. It  is  prepared  by  pouring  a  solution  in  distilled 
water  of  30  parts  of  crystallized  nitrate  of  silver  into 
another  solution  of  30  parts  of  neutral  chromate  of 
potassa,  also  in  distilled  water.    The  purple-red  pre- 


BED  COLORS. 


441 


cipitate  is  washed  with  distilled  water,  then  thrown 
upon  a  filter,  and  dried  in  the  dark. 

§  14.  Suljphide  of  antimony.    Vermilion  of  antimony. 

Lampadius  had  already,  in  1833,  proposed  for  a 
pigment,  the  red  sulphide  of  antimony,  which  covers 
well  when  employed  with  water,  but  which  possesses 
less  body  when  ground  in  oil.  Since  then,  several 
chemists  have  examined  this  sulphide  for  a  coloring 
substance,  but  we  shall  mention  only  those  experi- 
ments which  seem  useful  in  practice. 

Mr.  E.  Mathieu-Plessy  has  published  an  interest- 
ing memoir  on  the  vermilion  of  antimony  (^Bulletin 
de  la  8ociete  industrielle  de  MulJiouse,  vol.  26,  p.  297), 
from  which  we  give  an  extract : — 

"  The  product  to  which  I  give  the  name  vermilion 
of  antimony,  is  the  result  of  a  new  modification  of 
the  sulphide  of  antimony,  which  I  obtain  from  the 
decomposition  of  hyposulphite  of  soda  in  the  presence 
of  chloride  of  antimony. 

"  Among  the  phenomena  of  double  decomposition, 
so  characteristic  of  the  nature  of  mineral  substances, 
none  is  more  striking  than  the  production  of  the 
orange-yellow  sulphide  of  antimony  by  means  of  sul- 
phuretted hydrogen  or  of  an  alkaline  sulphide.  If 
the  latter  reagent,  from  long  exposure  to  the  air, 
be  partly  transformed  into  hyposulphite,  it  may  give 
with  a  protosalt  of  antimony,  according  to  its  greater 
or  less  degree  of  oxidization,  variously  colored  pre- 
cipitates. These  variations,  which  may  have  been 
observed  already,  will  be  easily  explained  by  the  re- 
action which  I  have  studied  out,  and  which  gave  me 
the  key  for  obtaining  a  red  sulphide  of  antimony  en- 
tirely distinct  from  the  following  well  known  ones : 


442 


MAlSrUFACTURE  OF  COLORS. 


"I  refer  to  the  orange-yellow  sulphide  produced 
by  the  reaction  of  sulphuretted  hydrogen  upon  the 
protochloride  of  antimony — the  black  native  sulphide 
— and  the  brown-red  sulphide,  a  modification  of  the 
preceding  one,  which  was  observed  for  the  first  time 
by  Fuchs,  and  has  recently  been  studied  by  Mr. 
Rose. 

"It  is  not  sufficient,  however,  to  put  the  proto- 
chloride of  antimony  and  the  hyposulphide  of  soda 
in  contact  with  each  other,  to  obtain  the  sulphide  of 
antimony  with  all  the  brightness  which  it  is  able  to 
acquire.  In  order  always  to  arrive  at  the  desired  re- 
sult, I  have  been  obliged  to  make  numerous  trials, 
and  to  vary  the  proportions  of  the  reagents  and  the 
temperature.  At  last  I  have  succeeded  in  finding 
out  a  process  which  is  satisfactory  in  regard  to  the 
quality  of  the  product  and  the  facility  of  its  pre- 
paration. 

"Believing  that  the  vermilion  of  antimony  might 
find  its  application  in  the  arts,  I  have  examined  its 
preparation  from  beginning  to  end,  and  I  have,  there- 
fore, aimed  to  produce  the  hyposulphite  of  soda  and 
the  chloride  of  antimony  on  a  manufacturing  scale. 
In  regard  to  the  hyposulphite  of  soda,  and  in  view  of 
avoiding  the  crystallizations  which  require  a  peculiar 
apparatus,  I  followed  a  process  which  gave  me  this 
salt  in  a  state  of  sufficient  purity,  at  a  time  when  its 
preparation  was  but  little  understood.  This  process 
was  based  upon  the  employment  of  the  sulphite  of 
soda. 

"  In  my  researches  I  have  demonstrated  that 
this  salt  should  be  employed  in  the  neutral  state, 
in  order  to  avoid  the  reaction  of  the  sulphurous 
acid  upon  the  hyposulphite,  resulting  in  the  Lang- 


RED  COLORS. 


443 


lois  salt,  which,  being  also  decomposed,  becomes 
sulphate  of  soda.  In  the  preparation  of  the  sul- 
phite I  have  followed  the  process  of  Mr.  Camille 
Koechlin,  which  consists  in  burning  sulphur  in  an 
apparatus  easily  established.  There  is  a  sieve  hold- 
ing large  crystals  of  soda,  which  is  suspended  in  a 
cask  opened  at  the  top.  The  bottom  is  connected  by 
means  of  a  pipe  with  a  small  clay  furnace,  upon  which 
the  sulphur  is  thrown  by  small  quantities  at  a  time. 

"The  combustion  of  the  sulphur  is  regulated  by 
means  of  a  trap-door ;  the  draft  is  good,  and  after 
two  or  three  days  the  crystals  of  soda  are  transformed. 
Should  there  be  portions  unacted  upon,  the  easily 
crumbling  sulphite  is  rubbed  off,  and  the  core  of  car- 
bonate is  replaced  in  the  cask.  A  solution  marking 
25°  Be.,  is  made  with  the  sulphite,  and  is  afterwards 
heated  and  saturated  with  crystals  of  soda.  When 
the  addition  of  this  salt  ceases  to  produce  an  effer- 
vescence (litmus  paper  does  not  give  sufficient  in- 
dications), or  rather,  when  a  diluted  sample  of  the 
liquor  produces  a  slight  disengagement  of  carbonic 
acid  by  the  addition  of  hydrochloric  acid,  then  sub- 
limed sulphur  is  put  in,  and  the  mixture  is  heated  for 
three  hours  upon  a  water-bath.  During  that  time 
the  evaporated  water  is  replaced,  and  the  mass  is 
frequently  stirred.  The  cold  liquor  is  diluted  with 
water,  so  as  to  mark  25°  Be. 

"The  protochloride  of  antimony  is  easily  prepared 
by  boiling  in  hydrochloric  acid  the  powdered  native 
black  sulphide  of  antimony.  When  the  disengage- 
ment of  hydrosulphuric  acid  begins  to  be  slow,  the 
whole  is  made  to  boil  for  a  few  minutes.  After  cool- 
ing, the  clear  liquid  is  decanted. 

"  In  order  to  obviate  the  inconvenience  of  the  pro- 


444 


MANUFACTURE  OF  COLOKS. 


diiction  of  sulphuretted  hydrogen,  the  gas  is  collected 
in  a  solution  of  soda,  or  it  is  burned  at  the  end  of  a 
glass  tube  connected  with  the  vessel,  where  the  re- 
action takes  place.  If  a  burning  alcohol  lamp  be 
placed  at  the  end  of  the  tube,  the  combustion  of  the 
gas  will  not  be  arrested,  even  should  the  gas  be 
accompanied  by  a  large  proportion  of  steam.  The 
chloride  of  antimony  thus  obtained  is  diluted  with 
water  to  25°  Be. 

"  The  two  solutions  of  antimony  and  of  hypo- 
sulphite being  prepared,  we  proceed  as  follows :  We 
pour  into  a  stoneware  vessel  4  litres  of  chloride  of 
antimony,  6  litres  of  water,  and  10  litres  of  hypo- 
sulphite of  soda.  The  precipitate  caused  by  the 
water  is  rapidly  dissolved,  in  the  cold,  by  the  hypo- 
sulphite. The  vessel  is  then  placed  in  a  hot- water 
bath,  where  the  temperature  of  the  mixture  is  gradu- 
ally raised.  At  about  30°  C.  the  precipitate  of  sul- 
phide begins  to  form  ;  it  is  orange-yellow  at  first  and 
becomes  darker  afterwards.  At  55°  C.  the  vessel  is 
removed  from  the  water  bath,  and  the  precipitate  is 
allowed  to  settle,  which  it  does  rapidly.  The  mother 
liquors  are  decanted,  and  the  deposit  is  washed  the 
first  time  with  water  holding  y\  of  hydrochloric  acid, 
and  afterwards  with  ordinary  water.  Lastly,  the 
precipitate  is  collected  upon  a  filter  and  dried.  The 
w^et  vermilion  of  antimony  is  of  an  exceedingly  bright 
red  color ;  after  drying  it  loses  part  of  its  brightness. 
This  pigment  may  be  prepared  in  the  cold,  but  the 
product  is  finer  and  more  constant  if  we  operate  in 
the  manner  just  described. 

''Being  certain  to  reproduce  my  new  sulphide 
whenever  it  is  desired,  I  have  undertaken  its  analysis. 
But  as  the  determination  of  the  antimony  is  very 


RED  COLORS. 


445 


difficult,  and  as  there  is  no  known  method  sufficiently 
accurate  for  the  purpose,  I  have  determined  the  sul- 
phur and  calculated  the  antimony  by  difference.  It 
has  also  been  necessary  to  determine  the  proportion 
of  water.  Moreover,  I  have  compared  the  orange- 
yellow  sulphide  with  my  own,  and  the  result  is — 

0.668  of  orange-yellow  sulphide  lose  0.038  at  200°  0. 
0.808  of  red  sulphide  lose     .       .     0.009  at  200°  C. 

"This  proves  that  the  vermilion  of  antimony  is  an 
anhydrous  substance,  the  above  loss  being  evidently 
due  to  an  imperfect  drying. 

"  There  now  remains  to  prove  by  analysis,  that 
the  vermilion  of  antimony  differs  from  the  orange- 
yellow  sulphide  by  only  one  equivalent  of  water. 
This  explains  the  new  properties  of  the  red  sulphide. 
I  have  found  by  analysis — 

Water  1.1 

Sulphur  26.7 

Antimony  (by  difference)    .       .  Y2.2 

100.0 

which  composition  proves  that  the  equivalents  of 
sulphur  and  antimony  are  in  the  ratio  of  3  to  1." 

M.  E.  Kopp  has  also  published,  in  the  Bulletin  de 
la  Societe  Industrielle  de  MulJiouse,  vol.  20,  page  379, 
a  memoir  on  the  manufacture  of  the  vermilion  of 
antimony.    "We  reproduce  the  following  extracts  : — 

"  The  sulphide  of  antimony,  according  to  its  physi- 
cal state  and  its  mode  of  preparation,  may  present 
very  varied  colorations.  It  is  crystalline  and  black- 
ish-gray in  the  native  state  and  melted.  Kept  in  the 
molten  state  for  a  long  time,  and  suddenly  cooled,  it 
becomes  hyacinth-red.  Precipitated  by  sulphuretted 
hydrogen  from  an  antimonic  solution,  it  is  of  an 


446 


MANUFACTURE  OF  COLOKS. 


orange  color  more  or  less  red.  In  the  kermes  state 
it  is  red-brown.  Lastly,  obtained  from  the  reaction 
of  a  soluble  hyposulphite  upon  the  chloride  of  anti- 
mony, its  red  color  is  more  or  less  bright,  and  more 
or  less  orange  or  crimson,  in  accordance  with  the 
temperature  employed,  and  the  concentration  of  the 
liquors. 

"This  latter  reaction  was  indicated  by  several 
chemists,  who  gave  recipes  for  the  regular  manufac- 
ture of  the  fine  red  sulphide  of  antimony,  which  was 
called  vermilion  of  antimony, 

"  All  of  these  methods  are  based  upon  the  employ- 
ment of  hyposulphite  of  soda  and  chloride  of  anti- 
mony in  quite  concentrated  solutions,  and  they  present 
various  inconveniences. 

'^In  the  process  which  I  have  followed,  the  ver- 
milion of  antimony  is  obtained  by  the  reaction  of  the 
chloride  of  this  metal  upon  a  dilute  solution  of  hypo- 
sulphite of  lime;  and  the  mother  liquors  are  used 
several  times,  and  are  thrown  away  only  after  they 
contain  too  great  a  proportion  of  chloride  of  calcium. 

'^I  am  now  going  to  describe  successively  the 
various  operations  in  the  manufacture  of  the  red  sul- 
phide of  antimony. 

"  1.  Preparation  of  the  Chloride  of  Antimony, — The 
decomposition  of  the  sulphide  of  antimony  by  hydro- 
chloric acid,  is  very  easy  in  experimental  laboratories, 
but  the  operation  presents  great  difficulties  when  we 
have  to  work  upon  large  quantities  of  materials. 

"After  a  series  of  experiments  (employment  of 
leaden  vessels,  heating  of  stoneware  vessels  in  sand 
and  pitch  baths,  etc.),  I  found  that  it  was  much 
better  to  roast  the  sulphide  of  antimony  at  a  mode- 
rate temperature,  and  with  the  contact  of  air  and 


RED  COLORS. 


447 


steam.  The  greater  part  of  the  sulphide  is  trans- 
formed into  oxide  of  antimony,  and  the  sulphurous 
acid  produced  is  used  in  the  manufacture  of  the  hypo- 
sulphite of  lime.  The  oxide  of  antimony  is  then 
easily  dissolved  in  commercial  hydrochloric  acid. 

"  If,  during  the  oxidation  of  the  sulphide  of  anti- 
mony, there  is  produced  a  certain  proportion  of  anti- 
monious  acid,  but  slightly  soluble  in  hydrochloric 
acid,  it  may  be  saved  by  collecting  the  residues  from 
the  treatment  with  hydrochloric  acid,  and  washing 
them  with  chloride  of  calcium  or  hyposulphite  of  lime, 
which  dissolves  the  adherent  chloride  of  antimony. 
They  are  then  dried  and  melted  with  a  certain  pro- 
portion of  sulphide  of  antimony  and  of  quicklime,  in 
order  to  transform  the  whole  into  antimony  green. 
The  addition  of  a  small  quantity  of  quicklime  is  in- 
tended for  decomposing  the  small  proportion  of  chlo- 
ride of  antimony  which  may  still  remain  in  the  residues. 

u  2  Preparation  of  the  Hyposulphite  of  Lime. — This 
salt  is  cheaply  prepared  by  the  action  of  sulphurous 
acid  upon  the  sulphide  or  polysulphide  of  calcium,  or 
the  oxy sulphide.  The  sulphurous  acid  is  produced 
by  the  combustion  of  brimstone,  or  the  roasting  of 
pyrites,  or  of  sulphide  of  antimony. 

"  The  polysulphide  of  calcium  is  prepared  by  boil- 
ing finely  ground  sulphur  with  newly  slaked  lime 
and  a  sufficiency  of  water.  It  is  advantageous  to  add 
to  this  solution  of  polysulphide,  a  certain  proportion 
of  powdered  oxysulphide  of  calcium,  which  is  the 
residue  of  the  lixiviation  of  crude  soda.  In  the  ab- 
sence of  oxysulphide,  quicklime  may  be  added. 

"  Sulphurous  acid,  in  its  reaction  upon  the  sulphide 
and  the  oxysulphide  of  calcium,  sets  sulphur  free,  and 
forms  a  sulphite  of  lime,  which,  in  presence  of  the 


448 


MANUFACTURE  OF  COLORS. 


sulphur  and  of  the  undecomposed  sulphide,  is  soon 
transformed  into  hyposulphite  of  lime.  The  reaction 
is  aided  by  the  elevation  of  temperature  which  takes 
place  in  the  apparatus. 

"The  liquor  is  examined  now  and  then  to  see 
whether  it  is  alkaline,  neutral,  or  acid.  As  soon  as 
it  has  become  slightly  acid,  it  is  run  from  the  appa- 
ratus into  a  large  settling  tank,  where  it  generally 
becomes  neutralized  by  a  certain  quantity  of  unde- 
composed oxy sulphide  of  calcium  held  in  it.  If,  after 
stirring  for  some  time,  the  liquor  preserves  its  acid 
reaction,  sulphide  of  calcium  is  added  until  complete 
neutralization,  which  is  ordinarily  made  apparent  by 
a  black  precipitate  of  sulphide  of  iron. 

"  After  settling  for  some  time,  the  clear  liquid  is 
decanted,  and  forms  a  solution  of  nearly  pure  hypo- 
sulphite of  lime.  The  same  vessel  is  subsequently 
used  for  neutralizing  the  liquors  obtained  during  the 
process  of  manufacture. 

3.  "  Preparation  of  Vermilion  of  Antimony. — The 
red  sulphide  of  antimony  is  prepared  with  the  above 
solutions  of  chloride  of  antimony  and  of  hyposulphite 
of  lime. 

"The  apparatus  is  simply  composed  of  several 
wooden  tanks,  holding  from  20  to  30  hectolitres  each, 
and  raised  about  1  metre  above  the  floor.  These 
tanks  are  so  arranged  that  they  may  be  heated  by 
steam,  either  through  a  copper  or  lead  pipe,  the 
opening  of  which  is  about  2  decimetres  from  the 
bottom,  or,  what  is  preferable,  through  a  coil  of 
pipes,  the  condensed  steam  of  which  may  be  carried 
outside,  without  being  mixed  with  the  liquors.  In 
this  manner  we  avoid  the  useless  dilution  of  the 
liquors  producing  the  vermilion  of  antimony. 


RED  COLORS. 


449 


"  When  the  pressure  of  the  boilers  has  reached  two 
or  three  atmospheres  the  tanks  are  filled  with  the 
solution  of  hyposulphite  of  lime  up  to  seven-eighths 
of  their  height.  We  then  pour  the  solution  of  chlo- 
ride of  antimony  into  the  first  tank,  2  or  3  litres  at  a 
time.  There  is  formed  a  white  precipitate  which  is 
rapidly  dissolved  at  the  beginning,  but  when  it  be- 
comes slow  of  solution,  even  by  stirring  the  liquor, 
the  addition  of  chloride  of  antimony  is  discontinued, 
because  there  must  always  be  a  certain  excess  of 
hyposulphite  of  lime. 

"  The  liquor  of  the  tank  should  be  perfectly  clear 
and  limpid,  and  any  white  precipitate  should  be  dis- 
solved by  adding  small  quantities  of  hyposulphite. 

"  Steam  is  then  let  in,  and  the  temperature  of  the 
liquors  is  gradually  raised  to  50°  or  60°,  or  even  70°  C, 
while  stirring  goes  on.  The  reaction  soon  becomes 
manifest ;  the  liquid  is  successively  colored  a  straw- 
yellow,  then  a  pure  lemon-yellow,  orange-yellow, 
orange,  reddish-orange,  and  lastly,  a  very  deep  and 
bright  orange-red.  The  steam  is  then  stopped,  and 
the  acquired  heat  of  the  liquid,  aided  by  a  slow 
stirring,  is  suflSicient  to  complete  the  reaction,  and 
impart  to  the  color  its  maximum  of  intensity.  Should 
the  heating  be  continued,  the  red-orange  color  would 
pass  successively  to  a  pure  red,  then  to  a  more  or 
less  crimson  red,  which  in  its  turn  would  grow  darker 
and  darker,  and  become  brown,  blackish-brown,  and, 
lastly,  nearly  black. 

"  We  see  that  by  graduating  the  temperature  it  is 
possible  to  obtain  all  the  intermediate  hues  between 
orange  and  brown-black.  The  tank  is  covered,  and 
the  colored  precipitate  is  allowed  to  deposit. 

"  The  clear  and  limpid  liquor,  which  smells  strongly 
29 


450  .  MANUFACTURE  OF  COLORS. 


of  sulphurous  acid,  is  decanted  through  holes  bored 
in  the  tank  at  different  heights,  and  is  conducted  by 
means  of  leaden  pipes  or  wooden  troughs  into  a  large 
reservoir  holding  a  certain  quantity  of  sulphide  and 
oxysulphide  of  calcium.  The  sulphurous  liquor  re- 
generates a  certain  proportion  of  hyposulphite  of 
lime. 

"As  the  solution  of  chloride  of  antimony  always 
contains  a  large  proportion  of  chloride  of  iron,  it  be- 
comes easy  to  watch  the  working  of  this  latter  ope- 
ration. All  the  iron  remains  soluble  in  the  mother 
liquors  of  the  sulphide  of  antimony,  and  as  soon  as 
they  are  brought  in  contact  with  the  sulphide  of  cal- 
cium, there  is  a  formation  of  insoluble  sulphide  of 
iron.  As  long  as  the  black  precipitate  remains,  the 
mother  liquors  charged  with  sulphurous  acid  have 
not  been  added  in  excess;  But  when  they  are  in  ex- 
cess the  black  precipitate  disappears,  since  it  is  trans- 
formed into  a  soluble  hyposulphite  of  iron.  The 
contents  of  the  reservoir  are  then  well  stirred,  and,  if 
necessary,  sulphide  of  calcium  is  added,  until  the 
black  precipitate  of  sulphide  of  iron  reappears  and 
remains  permanent.  At  the  same  time  a  certain  pro- 
portion of  hyposulphite  of  iron  should  remain  in  so- 
lution. This  condition  is  easily  fulfilled  when  we 
operate  upon  a  sufficiently  large  amount  of  materials. 
After  the  precipitate  has  settled  the  liquor  is  decanted, 
and  is  a  neutral  solution  of  hyposulphite  of  lime,  with 
a  certain  proportion  of  hyposulphite  of  iron  and  of 
chloride  of  calcium. 

"  We  should  carefully  avoid,  in  this  regeneration  of 
the  hyposulphite  of  lime,  leaving  in  an  excess  of  sul- 
phide of  calcium,  which  will  impair  the  coloration  of 
the  vermilion  by  causing  the  formation  of  the  ordinary 


EED  COLORS. 


451 


orange-yellow  sulphide  of  antimony.  Therefore,  if 
the  solution  of  hyposulphite  of  lime  be  yellow  and 
alkaline,  a  liquor  charged  with  sulphurous  acid  should 
be  added,  until  complete  neutralization  of  the  alkaline 
reaction. 

"  This  solution  of  hyposulphite  of  lime,  like  the 
first,  is  employed  in  the  preparation  of  a  new  quantity 
of  vermilion  of  antimony.  The  mother  liquors, 
charged  with  sulphurous  acid,  are  again  neutralized 
in  the  large  reservoir  by  a  new  proportion  of  sulphide 
and  oxysulphide  of  calcium,  and  soon,  until  the  liquors 
become  so  much  loaded  with  chloride  of  calcium  that 
it  becomes  necessary  to  throw  them  away,  or  to  re- 
serve them  for  some  other  purpose.  But  this  takes 
place  only  after  twenty-five  or  thirty  operations. 

"It  is  even  possible  to  save  the  sulphurous  acid  of 
these  worn-out  mother  liquors,  by  saturating  them 
with  a  milk  of  lime.  There  is  a  precipitate  of  oxide 
of  iron  and  of  sulphite  of  lime,  and  the  mother  liquors 
contain  only  chloride  of  calcium.  The  precipitate, 
mixed  with  sulphide  of  calcium,  is  transformed  by 
sulphurous  acid  into  the  hyposulphites  of  lime  and 
iron.  And  if  the  proportion  of  iron  be  too  great,  it 
may  be  precipitated  by  a  slight  excess  of  a  milk  of 
lime. 

"  The  precipitate  of  vermilion  of  antimony  left  on 
the  bottom  of  the  first  tank  is  received  into  a  conical 
cloth  filter,  and  the  drained  liquors  are  added  to  those 
of  the  reservoir.  The  tank  is  then  rinsed  with  tepid 
water,  which  is  made  to  pass  through  the  filter. 

"  The  washing  of  the  vermilion  should  be  done 
very  carefully,  and  it  is  often  necessary  to  empty  the 
contents  of  the  filter  into  a  large  volume  of  pure 
water,  and  to  wash  several  times  by  decantation.  The 


\ 


452  MANUFACTURE  OF  COLORS. 

red  sulphide  is  afterwards  filtered  again  and  dried  at 
the  ordinary  temperature,  or  in  a  stove-room,  the  tem- 
perature of  which  is  not  over  50°  to  60°  C. 

"  While  the  precipitate  is  settling  in  the  first  tank 
a  similar  operation  takes  place  in  the  second,  and  then 
in  the  third.  During  that  time  the  first  tank  has 
been  emptied,  and  its  mother  liquors  have  been  re- 
generated. These  are  then  brought  back  into  the 
first  tank,  and  another  precipitation  of  vermilion  of 
antimony  takes  place,  and  so  on. 

"  We  see  that  by  this  process  the  expense  in  sul- 
phur, and  therefore  in  sulphurous  acid  and  hyposul- 
phite, is  reduced  to  a  minimum. 

"  4.  Properties  of  the  Vermilion  of  Antimony, — The 
vermilion  of  antimony  is  in  the  state  of  a  very  fine 
powder,  without  taste  or  smell,  and  is  insoluble  in 
water,  alcohol,  or  essential  oils.  It  is  but  little  acted 
upon  by  the  weak  acids,  even  concentrated ;  or  by  the 
powerful  inorganic  acids  which  have  been  diluted  with 
water.  It  stands  the  latter  acids  better  than  the  ordi- 
nary sulphide  of  antimony.  Concentrated  and  hot 
hydrochloric  acid  dissolves  it,  when  sulphuretted  hy- 
drogen and  chloride  of  antimony  are  formed.  Nitric 
acid  oxidizes  it,  with  production  of  sulphuric  and 
antimonic  acids.  The  vermilion  of  antimony  is  not 
sensibly  acted  upon  by  ammonia  or  the  alkaline  car- 
bonates; on  the  other  hand,  the  powerful  caustic 
alkalies,  such  as  potassa,  soda,  baryta,  strontia,  and 
lime,  decompose  it  and  form  combinations  which  are 
colorless,  or  nearly  so.  The  color  is  therefore  de- 
stroyed, and  thus  we  see  that  this  pigment  should  not 
be  mixed  with  alkaline  substances.  A  high  tempera- 
ture blackens  it,  and  should  the  heat  be  such  as  to 
melt  it,  it  becomes  ordinary  sulphide  of  antimony. 


KED  COLORS* 


453 


"  The  vermilion  of  antimony  is  an  opaque  color, 
without  much  lustre  or  brightness,  when  it  is  mixed 
with  water,  thickened  by  gummy  or  gelatinous  sub- 
stances. On  the  other  hand,  when  ground  in  oil  or 
varnishes,  it  acquires  a  great  intensity  and  brightness 
of  color,  and  has  a  good  body  or  covering  power, 
being  superior  in  that  respect  to  red  lead,  orange 
mineral,  the  red  subchromate  of  lead,  and  cinnabar  or 
vermilion  with  a  basis  of  mercury.  A  well-prepared 
vermilion  of  antimony,  ground  in  oil,  gives  possibly 
the  purest  red  color,  that  is  to  say,  it  is  not  tinged 
orange,  or  pink,  or  crimson;  but  it  often  has  a 
brownish  hue.  It  is  perfectly  unalterable  by  air  or 
light,  and  may  be  mixed  with  white  lead,  which  is  not 
blackened  by  it,  even  after  several  years.  It  does 
not  assist  or  hinder  the  drying  of  oil.  Therefore,  the 
vermilion  of  antimony  is  a  pigment  especially  fitted 
for  oil  painting,  and  its  low  price  and  covering 
power  render  it  advantageous  for  carriage  and  house 
painting." 

§  15.  Sulpho-antimonite  ofharium, 

Mr.  E.  Wagner  has  indicated  the  sulpho-antimonite 
of  barium,  combined  with  the  artificial  sulphate  of 
baryta  (blanc  fixe),  as  furnishing  good  pigments  for 
painting. 

The  sulpho-antimonite  of  barium  is  prepared  by 
mixing — 

Finely  powdered  sulphate  of  baryta        .       .    2  parts. 
Native  gray  sulphide  of  antimony    .       .       .1  part. 
Powdered  charcoal  1  " 

and  calcining  the  mixture  at  a  red  heat  for  several 
hours  in  a  crucible  of  clay  or  graphite.  The  crucible 
should  not  be  opened  before  it  is  entirely  cold,  because 


454 


MANUFACTURE  OF  COLORS. 


the  carbonaceous  mixture  easily  becomes  inflamed. 
The  calcined  mass  is  then  boiled  in  water,  and,  as  the 
insoluble  residue  still  contains  undecomposed  sul- 
phate of  baryta  and  sulphide  of  barium,  it  is  mixed 
with  the  materials  of  another  operation. 

The  filtered  liquor  is  a  pale-yellow,  and  dilute  sul- 
phuric acid  is  added  to  it  until  the  orange  color  is 
entirely  precipitated.  Sulphuretted  hydrogen  is  dis- 
engaged. 

The  color  is  diluted  with  blanc  fixe.  If  a  purer 
orange  hue  be  desired,  the  solution  of  sulpho-anti- 
monite  of  barium  is  boiled  with  ^  part  of  sublimed 
sulphur.  The  sulpho-antimonite  of  barium  is  trans- 
formed into  sulpho-antimoniate,  which  has  a  composi- 
tion analogous  to  Schlippe's  salt.  If  the  1  iquor,  filtered 
from  the  undissolved  sulphur,  be  precipitated  by  sul- 
phuric acid,  we  obtain  a  mixture  of  blanc  fixe  and 
persulphide  of  antimony.  As  during  the  boiling  of 
the  liquors  a  part  of  the  sulphide  of  barium  is  trans- 
formed into  polysulphide,  there  is  always  in  the  pre- 
cipitate a  small  proportion  of  sulphur,  which  is  said 
to  be  productive  of  no  inconvenience. 

Instead  of  the  ordinary  sulphide  of  antimony  the 
vermilion  may  be  mixed  with  the  sulphate  of  baryta. 
The  mixed  pigment  will  be  obtained  at  once  by  em- 
ploying sulphuric  acid  for  the  decomposition  of  the 
hyposulphite  of  soda,  which  has  previously  been 
mixed  with  the  chlorides  of  antimony  and  barium. 

§  16.  Cobalt  pink. 

Cobalt  pink  is  a  mixture  of  the  oxide  of  this  metal 
with  magnesia.  It  is  a  durable  color,  and  more  or 
less  pink,  according  to  the  proportion  of  cobalt  it 
contains.    It  is  an  expensive  pigment,  which  is  used 


\ 

RED  COLORS. 


455 


only  for  fine  painting.  Its  preparation  consists  in 
making  a  paste  of  carbonate  of  magnesia  witli  a  con- 
centrated solution  of  nitrate  of  cobalt.  The  paste  is 
dried  in  a  stove,  and  then  calcined  in  a  porcelain 
crucible. 

§  17.  Arseniate  of  cobalt^  metallic  lime. 

This  salt  is  employed  in  oil  painting,  possesses  a 
very  deep  and  durable  red  hue,  and  is  found  native  in 
cobalt  mines  combined  with  other  substances.  These 
are  removed  by  a  treatment  with  boiling  nitric  acid, 
which  dissolves  the  pigment  and  the  other  impurities. 
The  clear  liquor  receives  small  additions  of  potassa 
until  all  of  the  iron  is  precipitated  as  arseniate;  then, 
after  settling  and  decanting,  a  further  addition  of 
potassa  precipitates  the  arseniate  of  cobalt. 

For  preparing  the  artificial  arseniate  the  sulpho- 
arsenide  of  cobalt  (gray  cobalt)  is  powdered,  mixed 
with  a  little  sand  and  twice  its  weight  of  potassa,  and 
then  fused  in  a  crucible.  There  is  produced  a  kind 
of  cinder  of  sulphides,  which  is  removed.  The  remain- 
ing white  arseniate  of  cobalt  is  pulverized  and  again 
fused  with  potassa.  The  new  cinders  formed  are 
removed,  and  the  button  of  pure  arsenide  is  powdered 
and  roasted,  in  order  to  transform  it  into  the  arseniate, 
the  deep-red  color  of  which  is  still  brightened  by  fine 
grinding. 

§  18.  Purple  of  Cassius. 

This  substance,  which  bears  the  name  of  its  inventor, 
is  the  precipitate  which  takes  place  when  solutions  of 
gold  and  chloride  of  tin  are  mixed  under  proper  con- 
ditions. The  preparation  of  the  purple  of  Cassius  is 
quite  difficult,  and  we  shall  explain  it  in  extenso,  in 


456 


MANUFACTURE  OF  COLORS. 


order  that  good  results  may  be  obtained.  We  should 
observe  that  a  pure  and  neutral  solution  of  proto- 
chloride  of  tin,  mixed  with  another  solution  of  neutral 
chloride  of  gold,  produces  maroon,  brown,  blue,  or 
green  precipitates,  and  sometimes  metallic  gold, 
according  as  the  liquors  are  more  or  less  concentrated. 
The  bichloride  of  tin  does  not  produce  a  precipitate 
with  the  solution  of  gold  ;  but  the  reunion  of  the  two 
chlorides  occasions  a  precipitate  of  a  purple  color. 
Oberkamps  has  observed  that  the  hue  is  the  more 
violet  as  the  proportion  of  chloride  of  tin  is  greater 
than  that  of  gold ;  and,  conversely,  that  the  hue  is 
pink  if  gold  be  in  excess. 

Buisson  recommends  the  following  process  for 
obtaining  a  fine  purple :  A  neutral  solution  of  proto- 
chloride  of  tin  is  prepared  by  dissolving  1  part  of  tin 
in  hydrochloric  acid.  On  the  other  hand,  2  parts  of 
granulated  tin  are  dissolved  in  an  aqua  regia  composed 
of  3  parts  of  nitric  acid  and  one  of  hydrochloric  acid, 
and  the  excess  of  acid  removed.  Lastly,  7  parts  of 
gold  are  dissolved  in  an  aqua  regia  made  of  1  part  of 
nitric  acid  and  6  of  hydrochloric  acid,  and  just  enough, 
and  no  more,  of  this  mixture  should  be  employed  for 
obtaining  a  neutral  solution.  The  solution  of  gold  is 
diluted  with  3|  litres  of  water,  receives  the  solution 
of  bichloride  of  tin,  and  then  the  protochloride  of  tin 
is  poured  in,  drop  by  drop,  until  the  precipitate  has 
acquired  the  desired  color.  An  excess  of  protochloride 
of  tin  imparts  a  bluish  hue.  After  settling,  the  pre- 
cipitate is  rapidly  washed  by  decantation,  and  dried 
in  the  dark. 

Buisson  ascertained  that  a  sample  of  purple,  pre- 
pared by  this  method,  was  composed  of — 


BED  COLORS. 


457 


Metallic  gold   285 

Bioxide  of  tin   659 

Chlorine   52 

Loss   4 

1000 

Oberkamps  has  found — 

In  violet  purple.      In  light  purple. 

Gold   0.398  0.795 

Oxide  of  tin    .       .       .       .    0.602  0.205 

Berzelius  has  obtained  from  a  purple  of  good 
quality — 

Gold   0.2835 

Bioxide  of  tin  .  .  .  .  0.6400 
Water   0.0765 

1.0000 

It  is  difficult  from  these  analyses  to  arrive  at  a 
conclusion  as  to  the  composition  of  the  purple  of 
Cassius.  In  a  more  recent  course  of  study  Mr.  L. 
Figuier  has  demonstrated  that  this  substance  is  a 
stannate  of  protoxide  of  gold,  which  may  be  obtained 
of  a  constant  composition  by  the  following  process  : — 

The  bichloride  of  gold  is  prepared  by  dissolving  20 
grammes  of  gold  in  100  parts  of  aqua  regia,  made 
with  4  parts  of  hydrochloric  acid  and  1  of  nitric  acid. 
The  solution  is  evaporated  to  dryness  in  a  water-bath, 
in  order  to  expel  the  excess  of  acid,  and  the  remaining 
chloride  of  gold  is  dissolved  in  750  grammes  of  water. 
Pure  granulated  tin  is  then  introduced  into  the  fil- 
tered liquor,  which,  after  some  time,  becomes  brown 
and  turbid.  After  standing  several  days  all  the  gold 
is  in  the  state  of  stannate  of  protoxide,  which  is  sepa- 
rated from  the  remainder  of  the  metallic  tin.  The 
product  is  collected  upon  a  paper  filter,  carefully 
washed,  and  dried  at  a  gentle  heat. 


458 


MA^^^UFACTURE  OF  COLORS. 


If  the  purple  remains  in  suspension  in  the  liquor, 
it  is  made  to  settle  by  the  addition  of  common  salt, 
and  a  slight  heating. 

The  separation  of  the  metallic  tin,  by  deeantation, 
should  be  done  carefully,  because  there  is  a  black  tin 
powder  which  settles  before  the  purple.  This  powder, 
which  contains  gold,  is  collected  apart  for  another 
operation. 

The  purple  of  Cassius  is  extensively  used  for  paint- 
ing on  porcelain ;  it  is  also  employed  in  miniature 
painting. 

§  19.  Madder  lake. 

Madder  is  the  name  of  the  ground  root,  and  alizari 
that  of  the  whole  root  of  a  plant  (Rubia  tinctormn)^ 
which  was  formerly  imported  from  the  East  and  from 
Holland,  but  which  is  now  successfully  cultivated  in 
several  French  departments. 

We  shall  not  in  this  work  try  to  give  all  the  char- 
acteristics by  which  the  madders  from  Holland,  Avig- 
non, and  the  East  are  recognized.  We  neither  believe 
that  it  is  of  advantage  to  indicate  the  various  trade- 
marks, because  these  marks  have  become  quite  illu- 
sory. The  best  is  to  trust  to  respectable  persons,  well 
acquainted  with  that  product,  or  to  learn  one's  self 
how  to  recognize  the  characteristics,  types,  and  quali- 
ties of  the  various  madders  found  in  the  trade. 

Madder  and  garancin  are  often  adulterated  with 
various  substances,  the  powder  of  tinctorial  woods, 
for  instance. 

Among  the  processes  generally  employed  for  ascer- 
taining the  presence  of  the  coloring  substances  added 
to  madder  or  garancin,  there  are  but  few  which  do 
not  require  a  good  knowledge  of  chemical  manipula- 


RED  COLORS. 


459 


tions.  It  is  very  difficult,  sometimes,  even  for  persons 
conversant  with  these  manipulations,  to  determine 
with  certainty  the  nature  of  the  foreign  substances, 
especially  when  the  adulteration  consists  of  a  mix- 
ture of  various  coloring  woods.  Mr.  J.  Pernod,  of 
Avignon,  has  communicated  to  the  Societe  Industrielle 
de  Mulhouse,  the  following  simple  and  practical  pro- 
cesses : — 

The  vegetable  powders  or  their  extracts,  employed 
for  the  adulteration,  may  be  divided  into  two  classes  : 
the  first  comprises  all  of  the  tinctorial  woods  which 
will  form  colored  compounds  with  alumina  and  the 
oxide  of  iron ;  such  are  the  woods  of  Brazil,  Campeachy, 
Cuba,  etc. 

The  second  class  comprises  all  of  the  substances 
holding  more  or  less  tannin,  with  or  without  coloring 
matter.  These  substances  do  not  make  colored  com- 
pounds with  alumina,  but  they  form  brown  or  black 
precipitates  with  the  oxide  of  iron. 

In  order  to  detect  in  madder  or  garancin  the  addi- 
tion of  a  small  proportion  of  the  various  coloring 
w^oods  of  the  first  class,  a  piece  of  white  paper,  from 
10  to  15  centimetres  square,  is  dipped  for  about  one 
minute  into  a  solution  of  bichloride  of  tin."^  It  is 
then  spread  upon  a  plate  or  a  sheet  of  glass,  and  dusted 
over,  by  means  of  a  sieve,  with  1  or  2  grammes  of  the 
powdered  sample.  After  half  an  hour,  all  the  points 
touched  by  the  particles  of  foreign  woods  will  present 
the  following  colorations:  crimson  red  spots  with 
Brazil  wood ;  violet  with  Campeachy ;  yellow  with 

*  This  is  the  tin-bath  of  the  dyers,,  obtained  by  dissolving  10 
parts  of  tin  in  a  mixture  of  25  parts  of  nitric  acid  and  55  parts  of 
hydrochloric  acid.  This  liquor,  for  use,  should  be  diluted  with 
twice  its  weight  of  water. 


460 


MANUFACTURE  OF  COLORS. 


Cuba  wood,  etc.,  while  the  portions  of  the  paper  in 
contact  with  the  madder  will  be  slightly  yellow. 

The  substances  of  the  second  class  are  detected  in 
this  manner  :  a  piece  of  writing  paper  is  immersed  in 
an  old  bath  of  protosulphate  of  iron,  part  of  which 
has  been  peroxidized,  or  in  a  fresh  one  to  which  a  few 
drops  of  neutral  nitrate  of  iron  have  been  added. 
After  being  dried,  the  paper  is  moistened  uniformly 
with  a  small  quantity  of  alcohol  (87  or  88  per  cent.), 
and  then  placed  upon  a  sheet  of  glass.  A  very  small 
quantity  of  the  suspected  powder  is  dusted  over  it  by 
means  of  a  fine  silk  sieve,  which  is  kept  very  near  the 
paper,  in  order  not  to  lose  by  a  current  of  air  any  par- 
ticle of  the  foreign  matters,  which  are  generally  finer 
than  the  madder.  After  a  quarter  of  an  hour  of  con- 
tact, there  are  blue-black  spots  on  the  points  touched 
by  the  adulterating  powder,  while  the  coloration  occa- 
sioned by  madder  is  rust-like  or  a  light-brown. 
When  the  alcohol  is  entirely  evaporated,  the  dust 
adhering  to  the  paper  is  rapidly  removed  with  water, 
and  the  blue-black  spots  due  to  the  combination  of 
the  tannin  with  oxide  of  iron,  become  still  more  appa- 
rent. 

Madder  does  not  entirely  abandon  its  red  coloring 
principle  to  cold  or  hot  water  ;  but  if  a  small  propor- 
tion of  alum  be  added,  an  intense  red  solution  is 
obtained,  which,  with  alumina,  may  produce  a  hand- 
some red  lake. 

1.  Eohiquet  and  Colin  Process, 

Eobiquet  and  Colin  have  indicated  the  following 
process :  2  kilogrammes  of  madder  are  macerated 
several  times  in  cold  water,  and  pressed  each  time. 
They  are  then  heated  for  three  hours  upon  a  water- 


RED  COLORS. 


461 


bath,  with  a  solution  of  1  kilogramme  of  alum  in  12 
litres  of  water.  After  filtration,  the  liquor  receives 
gradual  additions  of  a  solution  of  pure  carbonate  of 
soda,  until  the  precipitation  is  complete  ;  but  the  first 
portions  of  the  precipitate  are  collected  apart,  because 
they  are  finer.  All  the  precipitates  are  washed  until 
the  decanted  liquors  have  no  longer  an  acid  reaction ; 
they  are  then  drained  upon  a  filter,  moulded  into 
troches,  and  dried  in  the  open  air,  in  a  place  where 
there  is  no  dust. 

2.  Persoz  Pi'ocess. 

The  madder  is  fermented  or  washed  with  water  con- 
taining a  small  quantity  of  sulphate  of  soda.  It  is 
then  treated  for  15  or  20  minutes  with  ten  times  its 
weight  of  a  boiling  solution  of  alum  holding  one- 
tenth  of  alum.  The  liquor  is  strained  through  a 
filtering  bag,  and  when  its  temperature  has  been 
lowered  down  to  35°  or  40°  C,  it  is  neutralized  with 
carbonate  of  soda.  As  soon  as  cubic  alum  has  been 
formed  in  the  liquors,  these  are  brought  to  a  boil,  and 
there  is  formed  a  precipitate  of  a  tribasic  sulphate  of 
alumina,  which  carries  down  with  it  all  the  coloring 
matter.  The  lake  thus  produced  is  carefully  washed. 
This  lake,  in  the  opinion  of  Mr.  Persoz  is  superior  to 
all  others  on  account  of  not  being  gelatinous,  and 
being  therefore  easily  deposited,  washed,  and  col- 
lected. Moreover,  it  possesses  the  great  advantage 
for  dyeing  and  calico  printing,  of  being  quickly  dis- 
solved in  acetic  acid. 

The  madder  is  not  entirely  exhausted  by  this  ope- 
ration, and  it  may  be  treated  a  second  and  a  third 
time  with  alum.  The  resulting  liquors  are  generally 
reserved  for  working  madders  which  have  not  yet 


462 


MANUFACTURE  OF  COLORS. 


been  submitted  to  the  action  of  alum-water.  But,  if 
lakes  be  precipitated  from  them,  only  one-half,  or  even 
one-third,  of  the  carbonate  of  soda  necessary  to  satu- 
rate the  alum,  should  be  added. 

The  liquors  from  which  the  tribasic  sulphate  of 
alumina  has  become  precipitated,  should  not  be  thrown 
away.  They  are  used  boiling  for  dissolving  the  color- 
ing matter  which  may  remain  in  madder  or  its  residue. 
When  charged  with  coloring  principles,  they  are  again 
saturated  and  boiled,  and  a  new  quantity  of  colored 
lake  is  thus  obtained. 

In  all  dye-works,  the  whole  of  the  coloring  princi- 
ples of  madder  are  not  extracted,  and  there  are  always 
valuable  residua  which  may  be  worked  by  the  Persoz 
process,  or  by  other  methods.  But,  in  such  cases,  it 
is  not  necessary  to  ferment  the  madder,  or  to  wash  it 
with  sulphate  of  soda. 

Mr.  Persoz  has  also  indicated  another  mode  of  pre- 
paring madder  lake,  which  has  been  utilized  as  we 
shall  see  further  on.  For  the  saturation  of  the  alum 
liquor,  he  replaces  the  carbonate  of  soda  by  an  equiva- 
lent proportion  of  acetate  of  lead,  the  base  of  which 
is  immediately  precipitated  as  an  insoluble  sulphate. 
The  lake  thus  obtained  is  remarkable  for  the  purity 
and  the  intensity  of  its  color. 

3.  Lefort  Process. 

Mr.  J.  Lefort,  in  his  Cliimie  des  Couleurs,  has  de- 
scribed the  following  process  for  preparing  a  very 
fine  madder  lake  : — 

"  During  the  year  1827,  Eobiquet  and  Colin  dis- 
covered that  by  treating  madder  with  two-thirds  of  its 
weight  of  concentrated  sulphuric  acid,  there  was  pro- 
duced a  blackish  carbonaceous  substance,  in  which  all 


RED  COLORS. 


463 


the  red  coloring  principle  remained  unaltered.  This 
substance  is  now  common  in  the  market,  under  the 
names  of  garancin  and  sulphuric  charcoal  of  madder. 
Its  coloring  power  is  three  times  that  of  the  good 
qualities  of  madder ;  therefore  it  has  been  almost  en- 
tirely substituted  for  the  root  in  print  works. 

"  We  have  had  occasion  to  employ  garancin  in  the 
manufacture  of  lake,  and  with  the  following  results  : — 

"  1  kilogramme  of  garancin,  2  kilogrammes  of  alum, 
and  18  litres  of  pure  water  are  boiled  for  15  to  20 
minutes  in  a  well-tinned  kettle.  After  filtration,  and 
in  the  still  hot  liquors,  a  solution  of  carbonate  of  soda 
is  added  until  the  decoloration  is  complete.  By  col- 
lecting the  precipitate  at  different  periods,  the  lake 
obtained  at  the  beginning  of  the  operation  is  finer 
than  towards  the  end.  After  a  rest  of  several  hours, 
the  clear  liquid  is  decanted,  and  the  lake  is  thoroughly 
washed  until  the  water  runs  out  perfectly  clear  and 
tasteless.  The  precipitate  is  then  collected  upon 
cloth  filters  of  a  close  texture,  drained,  moulded  in 
troches,  and  dried  in  the  shade. 

"  We  have  every  reason  to  believe  that  the  greater 
part  of  the  fine  madder  lakes  employed  in  painting 
are  manufactured  from  garancin.  With  ascertained, 
but  variable  proportions  of  garancin,  alum,  and  water, 
we  may  precipitate  lakes  ranging  in  color  from  a  light 
pink  to  a  deep  red." 

4.  Khittel  Process. 

Mr.  J.  Khittel,  who  has  made  a  special  study  of 
the  preparation  of  madder  lakes,  has  indicated  in  the 
Technologiste^  vol.  20,  p.  340,  a  process  for  the  prepa- 
ration of  a  purple  madder  lake,  which  we  reproduce 
here. 


464 


MANUFACTURE  OF  COLORS. 


"  There  are  many  methods  and  recipes  for  preparing 
lakes  with  madder,  garancin,  alizarin,  etc.  ;  but  I  do 
not  believe  that  they  will  produce  an  article  which 
will  be  satisfactory  in  every  respect,  because  in  the 
greater  number  of  these  methods,  there  are  erroneous 
manipulations,  which  have  a  disastrous  influence  on 
the  quality  of  the  product,  and  diminish  its  value.  I 
have  undertaken  a  series  of  experiments  on  this  sub- 
ject, and  I  hasten  to  communicate  the  results. 

"  The  first  condition  in  the  preparation  of  a  lake, 
is  to  avoid  the  boiling  of  madder  or  any  of  its  solu- 
tions, because  there  are  formed  products  of  decompo- 
sition, and  the  lake  itself  is  wanting  in  brightness. 
In  the  preliminary  treatment  of  the  raw  material 
(madder  or  garancin),  we  should  also  eliminate  as 
completely  as  practicable  the  extractive  matters  and 
a  yellow  substance,  which  is  very  prejudicial.  The 
dissolving  agent  for  the  coloring  principle  is  gener- 
ally alum,  and  rightly  so ;  the  alum  solution  should 
be  employed  hot,  although  never  boiled  with  madder 
or  garancin.  I  have  several  times  treated  a  sample 
of  the  latter  substance  with  a  hot  solution  of  alum, 
while  another  portion  of  the  same  sample  was  boiled 
with  the  same  alum  solution.  In  every  case,  the 
lake  obtained  by  ebullition  was  inferior  to  that  result- 
ing from  the  first  mode  of  operation. 

"  Another  mistake  in  the  preparation  of  these  lakes, 
is  too  great  a  proportion  of  alum.  As  the  formation 
of  a  lake  is  based  upon  the  elimination  of  the  alumina, 
it  naturally  follows  that  the  greater  the  proportion  of 
alumina  in  the  liquor,  the  more  earthy  and  the  less 
bright  will  be  the  lake.  The  best  proportion  appears 
to  be  equal  weights  of  alum  and  madder  or  garancin. 
I  entirely  discard  the  employment  of  soda,  potassa. 


RED  COLORS. 


465 


and  alkalies,  by  which  the  alumina  is  precipitated  in 
the  hydrated  state.  This  use  of  alkalies  will  never 
result  in  a  satisfactory  lake,  because  the  alkali  itself 
modifies  the  coloring  substance,  and  the  lake  always 
has  a  violet  tinge. 

"  Mr.  Persoz  has  obtained  a  fine  lake  by  adding  to 
the  solution  of  alum  a  solution  of  subacetate  of  lead, 
then  filtering,  and  boiling  the  clear  solution.  I  have 
ascertained  that  this  process  is  the  best,  and  that, 
with  the  proper  care  during  the  operation,  satisfactory 
results  in  quality  and  quantity  will  be  obtained. 
Nevertheless,  I  have  made  the  following  modifica- 
tions : — 

"  Since  the  red  coloring  principle  of  garancin 
(rubiacin  and  alizarin  of  Higgin)  is  scarcely  soluble 
in  cold  solutions  of  the  alkaline  sulphates,  I  begin  to 
purify  the  garancin  with  solutions  of  the  crystallized 
sulphates  of  potassa  or  of  soda.  The  proportions 
which  I  have  found  the  most  satisfactory  are — 

Garancin  .1  kilogramme. 

Crystallized  sulphate  of  soda  ...    1  " 
Water  36  litres. 

"  The  garancin  is  put  into  the  water,  and  remains 
there  for  twelve  hours.  It  is  then  filtered,  pressed, 
and  again  put  into  pure  and  cold  water,  and  these 
operations  are  repeated  until  all  the  sulphate  of  soda 
is  expelled,  that  is,  until  the  washings  do  not  occasion 
any  turbidity  in  a  solution  of  subacetate  of  lead. 

"  A  quantity  of  alum  corresponding  with  that  of 
the  garancin  to  be  treated,  is  dissolved  in  from  ten  to 
twelve  times  its  weight  of  water,  and  boiled.  The 
washed  garancin  is  then  introduced  into  the  boiling 
solution,  which  is  removed  from  the  fire.  A  good 
proportion  is  1  kilogramme  of  alum,  1  of  garancin, 
30 


466 


MANUFACTURE  OF  COLORS. 


and  18  litres  of  water.  After  standing  for  fifteen  or 
twenty  minutes  the  solution  is  filtered,  and  the  resi- 
due of  garancin  is  washed  with  boiling  water.  When 
the  temperature  of  the  colored  extract  has  fallen  to  45° 
or  50°  C,  there  is  added  to  it  a  quantity  of  subacetate 
of  lead  equal  to  that  of  the  alum  employed,  and  the 
mixture  is  stirred  until  all  the  subacetate  is  trans- 
formed into  sulphate  of  lead.  The  colored  solution 
should  not  be  allowed  to  become  cold,  because  part 
of  the  color  might  be  precipitated.  After  settling, 
the  red  and  clear  liquor  is  easily  decanted  from  the 
heavy  precipitate  of  lead. 

"But,  as  this  lead  precipitate  contains  always  a 
small  proportion  of  coloring  matter  and  of  acetate  of 
alumina,  it  may  be  washed  with  hot  water,  which  n!ay 
be  used  for  dissolving  the  alum  in  a  subsequent  ope- 
ration. In  such  case,  the  following  proportions  will 
be  used  for  1  kilogramme  of  garancin  already  treated 
once : — 


Alum  . 

Subacetate  of  lead 
Water  . 


1  kilogramme. 
1  " 
18  litres. 


u  rpj^g  residue  of  washed  garancin  may  be  submitted 
to  a  second  similar  treatment,  but  the  proportions 
should  be  modified  as  follows  per  kilogramme  of 
garancin : — 

Alum  750  grammes. 

Subacetate  of  lead   750  " 

Water   .15  litres. 

"  Should  the  residue  of  garancin,  after  this  second 
treatment,  contain  enough  of  coloring  matter  to  cover 
the  expense  of  a  third  treatment,  we  should  employ 
for  each  kilogramme  of  garancin  twice  treated:— 


Alum 

Subacetate  of  lead 
Water 


RED  COLOES. 


467 

500  grammes. 
500  " 
12  litres. 


"  By  heating  for  some  time  nearly  to  the  point  of 
ebullition,  but  without  violent  boiling,  the  red  solu- 
tion separated  from  the  lead  precipitate,  there  is  sepa- 
rated a  purple-red  lake  which  is  much  superior,  in 
intensity  and  brightness  of  coloration,  to  all  the  lakes 
which  I  have  prepared  by  the  other  methods.  The 
acetic  acid  of  the  liquors  prevents  the  complete  pre- 
cipitation of  the  alumina  and  coloring  matter.  There- 
fore, after  the  first  lake  has  been  collected,  the  clear 
liquor  is  divided  into  two  equal  portions ;  into  one  of 
them  a  solution  of  carbonate  of  ammonia  is  poured 
drop  by  drop,  until  there  is  formed  a  slight  turbidity, 
but  not  a  precipitate.  The  two  portions  are  then 
mixed  and  heated  as  before,  and  another  quantity  of 
lake  is  obtained,  which,  however,  is  not  so  bright  as 
the  former. 

"  These  two  kinds  of  lake  are  easily  collected  and 
washed  upon  a  filter,  and  they  should  be  dried  at  a 
very  moderate  heat.  An  excess  of  alkaline  lye  dis- 
solves the  wet  lake,  and  becomes  colored  a  violet-red. 
It  is  also  dissolved  in  concentrated  acetic  acid,  and 
the  residue  of  its  calcination  upon  platinum  foil  is  a 
white-ash  of  alumina." 

5.  Lake  of  Garanceux, 

By  the  known  processes  of  dyeing,  and  when  ordi- 
nary madder  is  employed,  only  from  35  to  40  per  cent, 
of  its  coloring  matter  are  utilized.  The  residua  are 
therefore  very  rich,  and  of  late  years  have  been  used 
for  the  preparation  of  a  substance  called  garanceux. 
Several  methods  have  been  proposed,  but  we  shall 


468 


MAJiTUFACTURE  OF  COLORS. 


reproduce  here  only  that  published  by  MM.  Thierry- 
Mieg  and  Schwartz,  of  Mulhouse. 

After  dyeing,  the  madder-bath  is  mixed  with  dilute 
sulphuric  acid,  and  is  run  out  into  a  filter.  The  pro- 
portions are  :  3  kilogrammes  of  sulphuric  acid  at  66° 
Be.  for  400  kilogrammes  of  madder  used.  The  filter, 
which  may  be  a  pit  holding  a  layer  of  20  centimetres 
of  gravel  covered  with  packing  cloth,  retains  the 
coloring  matter  precipitated  by  the  acid.  The  liquor 
escapes  by  the  bottom,  which  is  also  covered  with 
packing-cloth.  The  residua  are  collected  and  put 
into  a  vessel  with  20  parts  of  water,  and  10  parts  of 
sulphuric  acid  at  52°  Be.,  for  100  parts  of  residua. 
Steam  is  admitted  into  the  mixture,  which  is  boiled 
from  four  to  six  hours.  After  filtration,  the  residue 
is  washed  five  or  six  times  consecutively  by  decanta- 
tion.  It  is  then  saturated  and  macerated  for  one  hour 
with  a  solution  of  1  to  2  kilogrammes  of  crystals  of 
soda,  and  poured  again  upon  a  finer  filter.  The  satu- 
ration is  complete  when  a  drop  of  the  mixture,  being 
deposited  upon  a  white  cloth,  produces  a  slightly 
pink  ring.  The  garanceux  remains  upon  the  filter^ 
and  after  being  pressed,  dried,  and  pulverized,  it  may 
be  used  again  in  dyeing. 

Should  the  garanceux  be  submitted  to  processes 
similar  to  those  emjDloyed  for  madder  and  garancin, 
it  seems  easy  to  prepare  from  it  madder  lakes. 

According  to  their  purity,  the  mode  of  preparatioUy 
or  the  adulterations,  there  are  in  the  market  many 
kinds  of  madder  lakes,  the  color  of  which  varies  from 
a  light  pink  to  a  purple  or  brown,  with  all  the  inter- 
mediary hues.  The  substances  generally  employed 
for  adulterating  madder  lakes,  are  the  lakes  of  car- 
mine and  of  red  woods. 


RED  COLOBS. 


469 


6.  Sacc  Process. 

Mr.  Sacc  has  prepared  very  fine  lakes  from  the 
pasty  alcohol  extract  of  madder.    Take — 

Pasty  extract  100  grammes. 

and  add 

Caustic  ammonia  50  " 

Water  125  " 

Macerate  for  twenty-four  hours,  and  add  the  same 
quantity  of  water  as  above.  Pass  through  a  silk 
sieve,  and  add  while  stirring  a  boiling  solution  of  100 
grammes  of  alum  in  one  litre  of  water.  This  lake  is 
of  a  magnificent  deep  red.  By  substituting  for  the 
alum  125  cubic  centimetres  of  a  solution  of  sulphate 
of  sesquioxide  of  iron,  marking  40°  Be.,  a  deep-violet 
lake  is  obtained. 

7.  Kopp  Process. 

Mr.  E.  Kopp  prepared  madder  lakes  by  a  process 
of  his  invention,  and  which  we  shall  describe  briefly. 

The  root  is  powdered  coarsely,  but  uniformly.  A 
solution  of  sulphurous  acid  is  then  prepared  by  the 
combustion  of  brimstone  or  of  pyrites,  or  by  the 
decomposition  of  sulphuric  acid  upon  charcoal.  In 
the  latter  method  from  6  to  8  kilogrammes  of  sul- 
phuric acid  produce  enough  of  sulphurous  acid  for  a 
solution  in  10  hectolitres  of  water. 

This  solution  holds  from  four  to  five  and  a  half 
thousandths  of  sulphurous  acid.  If  the  water  be  pure, 
from  a  half  to  one-thousandth  (in  volume)  of  commer- 
cial hydrochloric  acid  is  added  to  saturate  the  small 
proportion  of  earthy  carbonates  contained  in  certain 
kinds  of  madder,  that  of  Alsace  for  instance.  On 
the  other  hand,  calcareous  waters  require  a  larger 


470 


MANUFACTURE  OF  COLORS. 


addition  of  hydrochloric  acid  in  proportion  to  the 
quantity  of  carbonate  of  lime  present. 

The  madder  is  mixed  with  ten  times  its  weight  of 
sulphurous  solution,  and  the  whole  is  left  to  macerate 
from  twelve  to  twenty-four  hours  in  wooden  tanks, 
well  closed.  The  mixture  is  stirred  now  and  then. 
The  semi-fluid  substance,  with  the  rinsings  of  the  tub, 
is  then  poured  into  cloth  filters,  which,  after  drain- 
ing, are  gradually  but  strongly  pressed.  The  clear 
liquor  is  received  in  a  closed  wooden  vessel.  The 
pressed  madder  powder  is  removed  from  the  filter, 
and  again  treated  with  ten  times  its  weight  of  the 
sulphurous  solution.  The  filtered  liquor  is  added  to 
that  of  the  first  treatment.  Lastly,  the  residue  of 
madder  is  mixed  for  the  third  time  with  ten  times  its 
weight  of  sulphurous  solution ;  but  as  the  resulting 
liquor  is  poor  it  is  reserved  for  the  second  sulphurous 
treatment  of  another  portion  of  madder. 

The  madder  is  then  washed  with  boiling  water, 
pressed,  and  dried.  It  then  constitutes  a  weak  "  flower 
of  madder,"  which,  however,  will  produce  hues  of 
pure  color,  and  will  leave  the  body  ground  perfectly 
white.  It  may  be  left  wet  and  converted  into  a  weak 
garancin  by  processes  indicated  by  Mr.  Kopp. 

In  order  to  prepare  the  lakes  of  alizarin  and  purpu- 
rin,  which  are,  in  the  opinion  of  this  chemist,  the 
only  valuable  coloring  principles  of  madder,  the  above 
sulphurous  solution  is  employed. 

By  adding  to  this  solution  small  quantities  at  a 
time  of  acetate  or  hyposulphite  of  alumina,  or  of  alum 
neutralized  by  carbonate  of  soda,  and  keeping  the 
bath,  however,  with  an  acid  reaction,  and  hot,  we 
obtain  successive  precipitates  of  aluminous  lakes, 
which  present  the  following  characteristics  : — 


EED  COLORS. 


471 


First  lake  :  Dark  red  and  very  bright ; 
Second  lake :  Light  red  and  pleasing  brightness ; 
Third  lake :  Pink,  quite  pure  ; 
Fourth  lake:  Fink,  slightly  yellowish. 

The  concentrated  mother  liquors  are  of  a  dark- 
yellow  color,  and  dye  a  cloth  a  yellow,  somewhat 
fawn-colored.  Therefore,  in  the  opinion  of  Mr.  Kopp, 
it  results  that  the  liquor  contains  the  fawn-colored  or 
yellow  principle  of  madder,  after  the  precipitation  of 
alizarin  and  purpurin. 

Madder  lakes  are  employed  with  water  or  oil,  and 
their  greatest  consumption  is  for  miniature  painting 
and  calico  printing. 

8.  Adulteration  of  Lakes. 

We  have  already  given  some  information  as  to  the 
manner  of  testing  adulterated  madders;  but,  more 
recently,  Mr.  T.  Chateau,  in  a  memoir  on  the  adul- 
terations of  madder  and  its  derivatives,  which  received 
a  premium  from  the  Chamber  of  Commerce  of  Avig- 
non, has  indicated  the  following  processes  for  the 
detection  of  the  adulterations  : — 

"  Madder  lakes  are  falsified  according  to  their  color. 
When  red  or  jpink  the  adulteration  is  effected  with 
lakes  from  Brazil  woods.  The  violet  carmine  lakes  are 
adulterated  with  Prussian  blue  and  the  lakes  of  alka- 
net  and  Campeachy.  Black  madder  lakes  are  often 
mixed  with  the  black  lakes  of  logwood,  cochineal, 
sumac,  galls,  etc. 

A.  Red  and  Pink  Lakes. 

These  lakes  do  not  color  either  hot  or  cold  water. 
They  color  alcohol  and  ether  very  slightly,  and  only 
after  a  certain  length  of  time.  By  calcination  they 
leave  a  white  residue  of  alumina. 


472 


MANUFACTURE  OF  COLORS. 


"  Santaline. — If  the  lake  be  dark  it  may  contain 
santaline,  which  is  detected  by  the  orange-red  color 
acquired  by  the  ether  digested  with  the  suspected 
lake.  Alcohol,  under  the  same  circumstances,  would 
be  colored  red. 

"  If  the  lake  be  of  a  pink  hue  it  may  be  falsified  by 
lakes  of  Brazil  wood  or  of  cochineal.  But  as  madder 
lakes,  and  generally  all  lakes,  are  insoluble  in  water, 
ether,  or  alcohol,  their  coloring  substance  should  be 
insulated,  and  I  propose  the  following  method : — 

"  Every  lake  with  alumina  for  base  is  soluble  in  hy- 
drochloric acid,  or  in  acetic  acid  to  which  a  few  drops 
of  the  former  acid  have  been  added,  or  in  a  solution 
of  protochloride  of  tin.  After  the  lake  is  dissolved 
ether  is  added  to  the  solution,  and  the  whole  is 
shaken.  All  the  coloring  matter  is  dissolved  in  the 
ether,  which  will  acquire  different  colorations  accord- 
ing to  the  lakes  introduced. 

''Lakes  of  Brazil  wood, — First  process.  Let  us 
suppose  that  a  madder  lake  is  adulterated  by  the 
lakes  of  Pernambuco,  Sapan,  or  Brazil  wood,  the 
coloring  matter  will  be  rendered  soluble  in  ether  by 
the  process  indicated  above,  and  the  ether  will  be 
colored  a  gold-yellow. 

"  Venice  laJce,  ball  shape, — Second  process.  A  madder 
lake,  adulterated  by  Yenice  lake,  ball  shape  (one  of 
the  finest  lakes  of  Brazil  wood)  will  disengage  am- 
monia if  it  be  heated  in  a  test-tube  with  a  solution  of 
potassa.  Under  the  same  treatment  a  pure  madder 
lake  does  not  produce  ammonia. 

"Brazil  lake. — Third  process.  A  madder  lake, 
falsified  with  the  lakes  of  Brazil  wood,  will  be  gene- 
rally recognized  by  its  effervescence  with  the  acids, 
and  its  blue  coloration  by  iodine.    These  reactions 


RED  COLORS. 


473 


are  due  to  the  presence  of  chalk  and  starch,  which 
are  used  for  thickening  the  lakes  made  with  Brazil 
wood. 

"Carmine  lake, — Another  adulteration  of  madder 
lakes  is  that  with  the  so-called  carmine  lakes,  of  an 
inferior  quality.    This  fraud  is  easily  detected. 

"Water  is  not  colored  with  madder  lake,  while  it  is 
colored  with  carmine  lake.  The  coloration  is  imme- 
diate, and  becomes  more  intense  by  heating.  This 
aqueous  solution  of  carmine  lake  becomes  violet  by 
soluble  alkalies  and  gives  a  violet  precipitate  with 
lime-water,  chloride  of  tin,  sulphate  of  copper,  acetate 
of  lead,  and  sulphate  of  zinc. 

"All  that  has  been  said  about  red  and  pink  lakes 
may  be  applied  to  the  madder  carmine. 

B.  Violet  Lakes. 

"  The  violet  madder  lakes,  after  calcination,  leave 
an  ash  of  oxide  of  iron,  which,  being  dissolved  in 
hydrochloric  acid,  produce  an  abundant  precipitate 
of  Prussian  blue  by  the  addition  of  ferrocyanide  of 
potassium. 

"  These  lakes,  under  the  action  of  hydrochloric  acid, 
turn  a  dirty  orange-yellow  color. 

"  Campeacliy  laJces, — 1.  If  adulterated  with  Cam- 
peachy  lakes,  the  addition  of  hydrochloric  acid  will 
produce  a  crimson-red  coloration.  After  calcination, 
the  ash  will  be  nankin  yellow  or  white,  whether  the 
Campeachy  lake  is  partly  or  entirely  substituted  for 
that  of  madder. 

"2.  After  having  extracted  the  coloring  matter  in 
the  afore-mentioned  manner,  the  ether  is  colored  a 
gold  yellow,  and  will  give  the  Campeachy  reaction,  if 
that  substance  be  present. 


474  MA^^^UFACTURE  OF  COLORS. 

"AlJcanet — 1.  The  madder  lakes  falsified  by  alkanet 
lakes  are  easily  recognized.  The  lake  is  dissolved 
in  acetic  acid,  and  bisulphide  of  carbon  is  added,  which, 
after  shaking,  is  colored  an  intense  violet  red  if  al- 
kanet be  present.  This  reaction  is  characteristic  of 
that  substance. 

"2.  A  madder  lake  adulterated  by  alkanet  disen- 
gages violet  fumes  when  heated.  Moreover,  such  a 
lake  is  colored  blue  by  alkalies,  baryta,  and  lime. 

"  3.  After  solution  of  the  adulterated  lake  in  acetic 
acid,  and  separation  of  the  coloring  matter  in  ether, 
this  is  evaporated,  and  the  residue  is  treated  by  alco- 
hol, which  dissolves  the  coloring  principle  of  alkanet. 
This  alcoholic  solution  gives  a  magnificent  blue  pre- 
cipitate by  the  subacetate  and  the  acetate  of  lead, 
if  it  contains  anchusine. 

"  Orchil. — Orchil  lake  is  dissolved  in  hydrochloric 
acid,  which  becomes  red.  Ether,  shaken  with  this 
solution,  does  not  dissolve  a  trace  of  coloring  matter. 
The  same  reaction  takes  place  with  bisulphide  of 
carbon.  * 

'^Prussian  blue — Prussian  blue,  added  to  a  violet 
madder  lake  for  the  purpose  of  deepening  the  hue,  is 
recognized  by  the  addition  of  hydrochloric  acid,  which 
changes  the  violet  of  the  lake  to  a  green.  Hypo- 
chlorites, and  especially  hypochlorous  acid,  turn  the 
violet  to  a  blue. 

C.  Black  Lakes. 

"By  calcination,  these  lakes  give  an  ash  of  oxide 
of  iron.  Hydrochloric  acid  changes  them  by  degrees 
into  a  dirty  orange.  They  turn  a  brown  rusty  color 
by  the  action  of  protochloride  of  tin. 

"  Charcoal  and  lampblack, — These  lakes  being  of 


KED  COLORS. 


475 


a  fine  black  color,  it  is  possible  to  falsify  them  with 
finely  ground  charcoal  or  lampblack.  This  fraud 
will  be  detected  by  boiling  the  sample  with  hydro- 
chloric acid,  which  will  dissolve  the  lake,  and  will 
leave  the  charcoal  or  lampblack  as  a  residue. 

"Black  Camyeachy  lakes, — Black  madder  lakes  may 
be  mistaken  for  those  of  Campeachy.  The  latter  will 
redden  strongly  by  the  action  of  hydrochloric  acid 
and  of  the  protochloride  of  tin.  In  the  first  case, 
the  red  portions  will  stain  white  paper  a  cherry-red 
color ;  and  in  the  second  case,  a  more  or  less  violet 
red. 

"  Lake  with  cocMneal  basis, — In  order  to  distinguish 
a  black  madder  lake  from  one  with  cochineal  basis, 
an  addition  of  chloride  of  tin  will  turn  the  cochineal 
lake  a  cherry-red,  and  white  paper  will  be  stained. 
The  madder  lake  presents  no  such  reaction. 

"  Black  sumach  lake,  etc. — While  the  black  madder 
lakes  are  of  a  pure  color,  those  manufactured  from 
galls,  sumach,  and  other  astringent  substances  are 
olive-black.  I  do  not  believe  that  the  latter  can  be 
mixed  with  the  former,  on  account  of  the  olive  hue. 
Moreover,  the  adulteration  must  be  considerable,  in 
order  to  be  profitable." 

§  20.  Violet,  chocolate,  hrown,  and  red  lakes  of 
rhamnoxanthin  and  elder  herries. 

"When  the  boughs  of  several  kinds  of  buckthorn 
(Bhamnus frangula  and  Bha7nnus  catharticus)  are  ma- 
cerated for  three  or  four  days  in  bisulphide  of  carbon, 
according  to  Mr.  T.  L.  Phipson,  there  is  obtained  a 
gold-yellow  liquor,  which,  after  evaporation  at  the 
ordinary  temperature,  leaves  a  yellow  residuum. 
Alcohol  dissolves  the  coloring  principle  of  the  residue, 


476 


MANUFACTURE  OF  COLORS. 


and  leaves  behind  a  peculiar  fatty  substance,  which 
is  of  a  brown  color.  Lastly,  the  alcoholic  solution 
being  evaporated  to  dryness,  and  its  residue  treated 
by  ether,  there  are  deposited,  after  spontaneous  evapo- 
ration, crystals  of  a  substance  called  rhamnoxanthin. 

In  order  to  obtain  lakes,  it  is  not  necessary  to  ex- 
tract the  rhamnoxanthin  in  a  state  of  purity,  although 
it  is  the  real  coloring  principle.  The  boughs  of  the 
buckthorn  are  steeped  in  a  weak  ammoniacal  solu- 
tion, which  dissolves  the  coloring  matter,  and  fur- 
nishes a  purple-red  liquor,  which,  after  saturation  of 
the  ammonia  by  citric  acid,  and  the  addition  of  mag- 
nesia, produces  a  fine  violet  lake. 

If  protochloride  of  tin  be  added  to  the  decoction  in 
water  of  the  boughs,  and  the  liquor  be  precipitated 
by  carbonate  of  ammonia,  there  is  obtained  a  yellow- 
brown  lake,  which  becomes  of  a  chocolate  color  by 
the  action  of  sulphuric  acid. 

With  magnesia,  chloride  of  tin,  oxide  of  zinc, 
alumina,  and  oxide  of  lead,  it  is  possible  to  form  with 
rhamnoxanthin  a  number  of  brown,  red,  and  yellow 
lakes,  with  very  varied  hues. 

It  is  said  that  MM.  Depouilly  and  Neron  have 
obtained  very  handsome  violet  lakes,  by  treating 
elder  berries  (Samhucus  nigra  and  S,  ebulus)  in  the 
following  manner :  The  berries  are  pressed  in  order 
to  remove  the  seeds  and  the  juice,  and  to  collect  the 
pellicles,  which  contain  the  greater  part  of  the  color- 
ing matter.  These  pellicles  are  washed  in  cold  water, 
and  when  they  are  quite  clear,  they  are  boiled  in  the 
same  liquid,  in  order  to  obtain  colored  extracts,  which 
may  be  more  or  less  concentrated,  and  from  which 
are  prepared  lakes  for  painting  and  for  paper  hangings. 


BED  COLORS. 


477 


§  21.  Madder  carmine. 

Madder  carmine  is  an  exceedingly  bright  red  color, 
which  is  as  durable  as  that  of  madder  lake,  and  may 
be  substituted  for  the  same  hues  of  cochineal.  It  was 
discovered  by  Mr.  Bourgeois  in  1816,  and  is  still  pre- 
pared by  a  secret  process.  Nevertheless,  Mr.  Lefort, 
in  his  Chimie  des  Couleurs,  asserts  that  from  his  own 
researches,  a  very  fine  madder  carmine  may  be  ob- 
tained by  the  following  process : — 

Avignon  madder,  of  the  best  quality,  is  submitted 
to  a  kind  of  fermentation  in  a  wet  place.  When  it  is 
supposed  that  the  saccharine  and  bitter  mucilaginous 
substances  have  been  destroyed,  and  that  the  acid 
fermentation  begins,  the  madder  is  disintegrated,  and 
thrown  into  four  times  its  weight  of  sulphuric  acid, 
which  has  been  reduced  to  55°  Be.  by  an  addition  of 
water. 

"  The  vessel  in  which  the  mixture  is  made  should 
be  of  lead,  and  immersed  in  cold  water,  in  order  to 
avoid  too  great  an  elevation  of  temperature.  The 
paste  thus  obtained  is  left  to  stand  for  about  three 
hours.  It  is  then  diluted  with  4  or  5  parts  of  water, 
and  filtered  upon  a  layer  of  broken  glass,  placed  in  a 
lead  or  glass  funnel.  The  filtered  liquor  is  received 
in  a  large  volume  of  pure  water,  that  is,  free  from 
lime,  magnesia,  or  iron.  The  carmine  is  soon  pre- 
cipitated, and  it  is  collected  upon  a  paper  filter,  washed, 
and  dried  in  the  ordinary  manner." 

Madder  carmine  is  employed  especially  for  minia- 
ture and  other  artistic  painting. 

§  22.  Lalces  of  red  woods. 
The  red  woods  of  Brazil,  Santa-Martha,  Pernambuco, 
Sapan,  and  Lima  contain  a  coloring  matter,  of  a  fine 


478 


MANUFACTURE  OF  COLORS. 


crimson-red  color,  which  was  by  Mr.  Chevreul  called 
Bresilin,  It  may  be  precipitated  by  alumina  with  its 
natural  color,  but  it  changes  to  a  bright  pink  when 
a  certain  proportion  of  protochloride  of  tin  has  been 
added  to  the  solution. 

These  lakes  are  obtained  by  digesting  the  powdered 
woods  in  water  containing  tartrate  of  potassa, 

and  precipitating  with  a  solution  of  alum.  The  pre- 
cipitate is  collected  upon  a  filter,  washed  with  cold 
water,  and  dried.  Mr.  Girardin  says  that  the  results 
are  better,  if  the  decoction  of  Pernambuco  wood  be 
precipitated  by  a  solution  of  alum,  in  which  chalk 
and  starch  have  been  put  in  suspension.  The  colored 
paste  obtained  is  washed  with  cold  water,  drained, 
and  formed  into  lumps,  which  are  rendered  firm  by  a 
small  quantity  of  starch  paste,  and  of  rosin  dissolved 
in  essence  of  turpentine. 

The  Yenice  lake,  hall  shape,  according  to  the  same 
chemist,  may  be  prepared  by  kneading  a  mixture  of 
glue  and  gelatinous  alumina  in  a  concentrated  decoc- 
tion of  Brazil  wood,  until  the  desired  hue  is  obtained. 
The  coloration  is  brightened  by  alum,  and  a  violet 
reflex  is  imparted  by  soap. 

The  flat  laJce  of  Italy  is  a  fine  red  color  with  but 
little  durability.  It  is  said  to  be  a  combination  of 
alumina  and  lime  with  the  coloring  substances  of 
Pernambuco  or  Santa-Martha  wood. 

Mr.  G.  C.  Habich,  who  paid  a  great  deal  of  atten- 
tion to  the  manufacture  of  certain  colors,  has  pub- 
lished, on  the  lakes  of  red  woods,  an  article  which  is 
too  important  to  be  overlooked,  and  is  as  follows : — 

"  The  precious  coloring  substances,  furnished  by 
tbe  woods  of  Pernambuco,  Lima,  Santa-Martha,  Sapan, 
etc.,  are  all  soluble  in  pure  water.    If  these  woods  are 


RED  COLOKS. 


479 


treated  with  boiling  water,  their  coloring  matter  is 
dissolved  in  combination  with  ammonia.  Does  am- 
monia exist  in  these  dye  woods,  or  is  it  a  product  of 
the  destruction  of  vegetable  albumen?  I  shall  not 
try  to  answer  this  question  at  the  present  time.  The 
presence  of  this  ammonia,  in  the  case  of  dyeing  and 
preparing  colors,  is  disadvantageous,  because  it 
facilitates  the  solution  of  certain  brown  substances, 
similar  to  humin,  which  tarnish  the  brightness  of  the 
colors.  But  as  these  humic  substances  are  not  solu- 
ble in  water  free  from  ammonia,  we  understand  that 
they  may  be  eliminated  by  a  purification  or  a  clarifi- 
cation of  the  colored  decoctions.  On  that  account, 
and  in  former  times,  it  was  usual  for  manufacturers 
of  colors  to  let  the  decoctions  stand  for  a  long  time. 
The  small  proportion  of  sugar  held  by  them  was,  by 
fermentation,  transformed  into  alcohol ;  the  alcohol 
was,  in  its  turn,  transformed  into  acetic  acid,  which 
combined  with  the  ammonia,  and  determined  the  pre- 
cipitation of  the  brown  matter.  The  red  coloring 
principle,  useful  for  the  preparation  of  red  lakes, 
remained  therefore  in  solution  with  another  deep 
yellow  substance,  and  this  solution  was  decanted 
from  the  deposit.  This  process,  as  we  perceive,  is 
very  slow  and  takes  several  weeks.  I  have  arrived 
at  the  same  result  by  employing  pure  hydrochloric 
acid. 

"  The  acid,  diluted  with  an  equal  volume  of  water, 
is  introduced  in  a  stream,  of  the  size  of  a  straw,  into 
the  decoction  of  red  wood,  which  is  kept  stirred  all 
the  while.  The  addition  of  acid  is  stopped  when  a 
filtered  sample  of  the  liquor  has  become  yellow.  The 
mixture  is  then  stirred  every  half  hour.  The  clarifi- 
cation is  generally  complete  in  a  few  days.    The  clear 


480 


MANUFACTURE  OF  COLORS. 


liquor  is  decanted,  and  the  deposit  is  washed  upon  a 
filter.  This  purified  decoction  is  then  used  for  the 
preparation  of  red  lake,  which  contains  the  coloring 
substance  combined  with  alumina  and  oxide  of  tin. 
I  shall  not  describe  the  manufacture  of  the  aluminous 
lakes,  known  under  the  names  of  crimson  lake,  lake 
in  ball,  Yienna  lake,  etc.,  because  the  processes  of 
preparation  have  been  often  described,  and  because 
the  results  are  always  good  when  the  alumina  salt 
employed  is  free  from  iron.  I  prefer  giving  some 
particulars  in  regard  to  the  red  Florentine  lake, 
which  is  of  a  bright  carmine-red,  and  is  sought  for 
by  manufacturers  of  fancy  and  mottled  papers. 

"  This  fine  color,  which,  unhappily,  does  not  resist 
the  action  of  light,  is  a  combination  of  the  coloring 
principle  with  the  binoxide  of  tin.  A  combination 
may  also  take  place  with  the  protoxide  of  tin,  but  it 
is  crimson,  and  without  brightness.  The  manufac- 
turer of  colors  should,  therefore,  pay  great  attention 
to  the  preparation  of  the  tin  solution,  which  should 
contain  no  protoxide  or  the  corresponding  chloride. 
The  preparation  of  the  proper  solution  will  be  certain, 
if  we  are  guided  by  the  following  instructions  : — 

"  The  commercial  tin  salt  is  generally  very  impure, 
and  it  becomes  absolutely  necessary  to  prepare  the 
tin  solution  on  the  spot.  The  purest  English  tin  is 
melted,  and  transformed  into  irregular  ribbons  by  the 
known  process,  that  is,  by  letting  it  run  from  a  height 
of  about  2  metres,  into  water  which  is  being  moved  in 
a  circular  direction.  This  tin,  which  presents  a  very 
extended  surface,  is  put  into  two  stoneware  pots,  one 
of  which  is  filled  with  hydrochloric  acid,  free  from 
iron,  and  marking  from  20°  to  25°  Be.  After  twenty- 
four  hours,  the  acid  is  decanted  into  the  second  pot. 


RED  COLORS. 


481 


and  the  metal  remaining  in  the  first  pot  is  left  ex- 
posed to  the  oxidizing  action  of  atmospheric  air. 
After  twenty-four  hours,  the  liquor  of  the  second 
pot  is  poured  into  the  first  one. 

"In  order  to  transform  this  protochloride  of  tin 
into  perchloride,  the  solution  and  an  equal  volume 
of  the  same  hydrochloric  acid  are  poured  into  a 
much  larger  vessel,  holding  six  times  as  much,  and 
immersed  in  a  boiling  water  bath.  If,  then,  nitric 
acid  be  added  by  small  portions  at  a  time,  a  tumult- 
uous decomposition  takes  place,  with  production  of 
red  vapors.  The  reaction,  which  requires  a  few 
minutes,  should  be  finished  before  a  new  quantity  of 
nitric  acid  is  added;  indeed,  rapid  additions  of  acid 
may  cause  the  liquor  to  run  over.  As  a  precaution 
against  such  an  accident,  the  vessels  and  the  water 
of  the  bath  should  be  perfectly  clean,  so  as  to  be  able 
to  recover  (in  a  diluted  state)  any  liquor  which  may 
run  over. 

"  These  additions  of  acid  are  continued  as  long  as 
there  is  a  strong  effervescence.  When  the  reaction 
shows  signs  of  moderation,  it  becomes  necessary  to 
test  with  reagents  the  exact  point  of  transformation, 
but  before  the  tests  are  applied,  the  production  of 
red  vapors  must  have  ceased. 

"As  a  reagent,  we  may  use  a  solution  of  hydrosul- 
phuric  acid,  which  should  not  produce  any  brown 
precipitate  in  a  sample  of  the  liquor.  The  precipitate 
may  be  a  light  yellow  with  hot  liquors.  Sulphurous 
acid  should  produce  no  precipitate  whatever. 

"  When  all  the  tin  has  been  transformed  into  per- 
chloride,  the  liquor  is  allowed  to  become  clear,  and 
we  proceed  to  the  precipitation  of  the  coloring  sub- 
stance. The  solution  of  tin  is  added  to  the  colored 
31 


482 


MANUFACTURE  OF  COLORS. 


liquor,  which  is  kept  stirred  until  a  drop  of  perchlo- 
ride  of  tin  fails  to  produce  a  pink  cloud  in  a  sample 
of  the  liquor.  The  mixture  is  then  stirred  for  half  an 
hour. 

''The  proportion  of  perchloride  of  tin  depends 
naturally  upon  that  of  the  coloring  matter.  After 
having  determined  the  amount  by  a  preliminary  trial, 
an  equivalent  proportion  of  perchloride  of  tin  is  poured 
into  the  colored  liquor,  and  after  a  stirring  of  half  an 
hour,  another  final  test  is  applied  in  order  to  see 
whether  the  precipitation  is  complete. 

"  After  decantation  of  the  clear  liquor,  the  color  is 
washed  with  pure  water.  Should  the  water  employed 
be  calcareous,  it  should  be  rendered  slightly  acid  with 
hydrochloric  acid.  This  precaution  is  necessary, 
otherwise  the  washings  may  impair  the  brightness  of 
the  color. 

"  If  the  color  is  to  be  sold  in  paste,  for  instance,  to 
manufacturers  of  fancy  papers,  there  should  be  mixed 
with  it  none,  or  very  little,  of  earthy  substance.  But 
if  it  be  desired  to  produce  a  substantial  color  for 
theatrical  painting,  a  certain  proportion  of  finely 
ground  plaster  of  Paris  or  alabaster,  free  from  iron, 
is  added.  Many  kinds  of  plaster  of  Paris  contain  a 
small  proportion  of  carbonate  of  lime,  which  will  im- 
pair the  brightness  of  the  color;  but  this  inconven- 
ience may  be  remedied  by  a  washing  with  dilute 
hydrochloric  acid." 

A  skilful  manufacturing  chemist  has  published  in 
the  London  Journal  of  Arts,  a  new  process  for  the 
manufacture  of  lakes  from  dye  woods,  which  it  is 
interesting  to  reproduce  here,  and  is  as  follows : — 

''It  is  possible  with  the  salts  of  antimony,  and 
preferably  with  the  chloride,  to  precipitate  the  color- 


RED  COLORS. 


4S3 


ing  matter  of  certain  dyestuffs,  such  as  Sapan  wood, 
logwood,  cochineal,  quercitron  bark,  etc.,  and  to 
obtain  certain  colors,  known  under  the  name  of  lakes, 
which  have  been  prepared,  up  to  the  present  time, 
with  other  metallic  salts. 

"In  order  to  manufacture  a  red  lake,  the  following 
substances  are  employed  : — 

"  To  5  litres  of  chloride  of  antimony,  marking  80° 
of  the  hydrometer  of  Twaddle,  add  100  litres  of  a  clear 
decoction  of  Sapan  or  Lima  wood,  marking  7°  Twad- 
dle. The  whole  is  carefully  stirred,  and  allowed  to 
deposit  for  several  hours,  and  is  then  filtered.  The 
precipitate  is  washed  twice,  each  time  with  20  litres 
of  water.  After  its  draining,  the  lake  is  finished,  and 
may  be  dried  or  sold  in  paste.  With  more  diluted 
decoctions,  the  washings  are  not  necessary. 

"  The  proportions  above  indicated  may  vary  accord- 
ing to  the  intensity  of  hue  desired.  With  a  greater 
proportion  of  chloride  of  antimony,  the  color  will 
have  a  crimson  hue ;  and  if  the  proportion  of  the  de- 
coction of  Sapan  wood  be  increased,  the  hue  will  tend 
towards  a  scarlet. 

"The  same  processes  are  followed  for  obtaining 
purple  and  violet  lakes ;  but  in  this  case,  the  Sapan 
wood  is  replaced  by  that  of  Campeachy  (logwood). 
The  following  proportions  give  good  results  ;  5  litres 
of  chloride  of  antimony,  marking  80°  Twaddle,  and 
75  litres  of  a  well-settled  decoction  of  Campeachy, 
marking  6°  Twaddle. 

"  In  the  preparation  of  yellow  lakes,  Sapan  wood  is 
replaced  by  quercitron  bark. 

"  In  the  same  manner  it  is  possible  to  obtain  lakes 
with  all  the  dye  drugs  which  form  colored  precipitates 
with  the  salts  of  antimony." 


484 


MANUFACTURE  OF  COLORS. 


§  23.  Yegetahle  violet 

The  vegetable  violet  is  a  lake  which  results  from 
the  combination  of  hcematoxylin,  the  coloring  princi- 
ple of  logwood,  with  alum  and  acetate  of  lead.  It 
possesses  a  fine  violet  color,  which,  however,  does  not 
resist  the  action  of  light,  and  which,  in  the  liquid 
state,  should  be  preserved  in  tightly  closed  bottles  of 
black  glass. 

It  is  prepared  by  dissolving  300  grammes  of  alum 
in  1  litre  of  hot  water,  and  adding  250  grammes  of 
crystallized  acetate  of  lead,  dissolved  in  a  small 
quantity  of  water.  Sulphate  of  lead  is  precipitated 
while  a  portion  of  the  acetate  remains  in  solution 
with  the  salt  of  alumina.  On  the  other  hand,  a  de- 
coction of  600  grammes  of  logwood  (Campeachy)  is 
made  in  5  litres  of  water,  which,  after  cooling,  is  fil- 
tered through  a  cloth.  To  100  parts  of  this  decoc- 
tion of  logwood,  10  parts  of  the  mixture  of  acetate 
of  lead  and  salt  of  alumina  are  added,  and  afterwards 
a  solution  of  gum  Arabic,  the  proportion  of  which 
varies  with  the  hue  desired. 

§  24.  Cartliamus  red,  Carthamin.  Carthamic  acid. 
Vegetable  red.  SjpanisJi  red.  Bed  in  plates,  Por- 
tuguese red.    Leaf  red,    Chinese  rouge  for  the  face, 

Carthamus  red  is  the  red  coloring  principle  of  the 
flosculous  flowers  of  a  plant  {Carthamus  tinctorius) 
called  carthamus,  safflower,  German  safiron,  safra- 
num,  etc.,  which  is  very  different  from  the  oriental 
saffron,  and  which  is  cultivated  in  France  and 
Germany. 

This  red  coloring  principle  is  by  chemists  called 
carthamin  or  carthamic  acid ;  it  is  in  the  plant  united 


RED  COLORS. 


485 


with  a  yellow  coloring  substance,  which  is  soluble 
in  water,  while  carthamin  is  insoluble. 

The  color  of  carthamus  used  for  rendering  yellow 
the  floors  of  dwellings,  is  a  lake  principally  made  of 
the  yellow  coloring  principle.  It  is  prepared  by  boil- 
ing carthamus  in  water  holding  a  small  quantity  of 
alum,  and  adding  curcuma  (turmeric)  for  bright- 
ening the  tone  of  the  color.  The  yellow  solution  is 
employed  for  diluting  the  size. 

The  flowers,  which  have  been  thus  deprived  of  the 
yellow  principle  by  means  of  alum-water,  or  what  is 
better,  by  water  acidulated  with  acetic  acid,  contain 
only  the  red  principle,  and  are  ready  for  the  extrac- 
tion of  the  carthamus  red.  *  They  are  worked  with 
their  own  weight  of  cold  water  holding  from  15  to  16 
per  cent,  of  carbonate  of  soda.  The  liquor  is  filtered 
upon  a  cloth,  and  the  same  manipulation  is  repeated 
•two  or  three  times.  The  flowers  are  then  thrown 
away.  The  liquors  are  collected  in  a  wooden  tub, 
filled  with  pieces  of  woollen  or  cotton  cloth,  which 
absorb  the  carthamin.  These  cloths  are  then  well 
washed  in  pure  water,  and  the  color  is  removed  by  a 
solution  holding  10  per  cent,  of  carbonate  of  soda, 
which  dissolves  it.  The  color  is  again  precipitated 
by  a  solution  of  pure  citric  acid.  The  flakes  of  pre- 
cipitated carthamin  are  washed  several  times  with 
cold  water,  then  collected  upon  a  filter,  and  dried  in 
a  dark  place. 

The  dry  carthamus  red  has  a  fine  purple-red  metallic 
lustre  when  it  is  in  thin  layers,  but  a  large  quantity 
of  it  appears  green.  Its  hue  may  vary  from  a  red  to 
a  pink,  according  to  its  quality  and  its  state  of  com- 
minution. This  color,  which  is  always  very  expen- 
sive, is   employed   by  manufacturers   of  artificial 


486 


MAN^UFACTURE  OF  COLORS. 


flowers,  for  the  imitation  of  flesh  color  in  colored 
prints,  by  perfumers  for  the  preparation  of  face  pow- 
ders, and  also  by  dyers.  It  is  to  be  regretted  that  it 
is  not  fast,  and  that  it  does  not  unite  well  with  the 
liquid  vehicles  used  in  painting. 

§  25.  Indian  red. 

Professor  Dussauce  has  published  in  the  Teclmolo- 
giste,  June,  1861,  an  article  upon  a  new  red  vegetable 
color,  which  we  reproduce  here. 

"  Painters,"  says  he,  "  use  but  a  small  number  of 
colors  of  organic  origin,  and  those  employed  are 
generally  in  the  state  of  lakes,  that  is,  of  combina- 
tions of  a  coloring  principle  with  a  metallic  oxide 
or  a  salt.  During  my  researches  upon  the  coloring 
principles  of  vegetable  origin,  I  have  obtained  from 
sandal  wood  (sanders)  a  substance  which  is  nearly 
equal  to  carmine  in  beauty  and  brightness. 

"  This  principle  is  durable,  of  a  pure  red,  and  melts 
at  a  temperature  a  little  below  100°  C.  An  increase 
of  heat  decomposes  it.  It  is  insoluble  in  water  and 
the  fixed  oils,  but  very  soluble  in  alcohol,  ether,  acetic 
acid,  and  the  essential  oils.  Dry  chlorine  has  no 
action  upon  it,  but  wet  chlorine  destroys  it.  Acids 
do  not  change  it,  except  nitric  and  chromic  acids,  and 
those  rich  in  oxygen.  It  stands  sulphuretted  hydro- 
gen, light,  and  air  well.  Altogether  it  is  a  very 
durable  vegetable  color. 

"Its  preparation  is  very  simple.  Powdered  red 
sandal  wood  is  macerated  with  alcohol,  and  the  alco- 
holic solution  is  treated  with  hydrated  oxide  of  lead 
in  excess.  The  resulting  precipitate  is  collected  upon 
a  filter,  washed  with  alcohol,  and  dried.  It  is  then 
dissolved  in  acetic  acid,  and  precipitated  again  by  an 


RED  COLORS. 


487 


addition  of  water  in  which  it  is  insoluble.  The  acetate 
of  lead  remains  in  solution,  and  may  be  used  for  the 
preparation  of  the  hydrated  oxide  of  lead.  The  pre- 
cipitate is  again  carefully  washed  with  water,  and 
dried  at  a  low  temperature. 

"  It  would  require  too  much  space  to  give  here  all 
the  researches  by  means  of  which  I  came  to  the  con- 
clusion that  this  color  was  pure  santalin.  Its  price 
will  not  be  over  10  francs  per  kilogramme,  and  I  in- 
tend to  prepare  for  dyers  and  printers  a  santalin 
compound  which  may  be  dissolved  in  water,  a  thing 
not  hitherto  discovered." 

§  26.  Cochineal  carmine. 

Cochineal  is  a  small  insect  of  the  genus  IIemi;pter^ 
and  of  the  family  of  the  gall  insects,  called  by  Linnaeus 
Coccus  cacti.  This  insect  is  originally  from  Mexico, 
but  it  is  now  successfully  raised  in  the  Canaries,  in 
India,  Spain,  and  Algeria.  It  feeds  upon  the  nopal 
Cactus  coccinilifer^  L. 

Cochineal,  from  the  analysis  made  by  Pelletier  and 
Caventou,  is  composed  of  carmine  or  pure  coloring 
principle ;  coccine  or  raw  animal  coloring  material ; 
stearin  and  olein ;  phosphate  and  carbonate  of  lime  ; 
chloride  of  potassium,  phosphate  of  potassa,  and 
potassa  united  with  an  organic  substance. 

In  the  trade  cochineal  is  distinguished  by  the  names 
of  the  countries  from  which  it  comes,  Vera  Cruz, 
Honduras,  Canaries,  and  India  ;  and  each  division  is 
subdivided  into  types  having  each  a  gradation  of 
hues.  For  instance,  there  is  the  black  cochineal  or 
zacatille,  the  marble  or  silvered  cochineal,  and  some- 
times the  pinkish  and  wild  cochineal.  Each  of  the  first 
three  types  is  subdivided  into  fine,  good,  ordinary. 


488 


MANUFACTURE  OF  COLORS. 


commercial,  and  sometimes  low  commercial.  Drug 
brokers  base  themselves  upon  the  following  examina- 
tions in  establishing  the  grades  of  quality:  1.  They 
examine  the  size,  shape,  and  conformation  of  the 
insect,  which  is  said  to  be  hollow  or  filled  according 
as  the  lower  face  is  concave  or  level.  If  the  edges 
are  wrinkled,  it  is  said  to  be  curled.  2.  The  powder, 
from  the  greater  or  less  beauty  of  its  color,  is  a  good 
index  of  its  tinctorial  value.  3.  Lastly,  the  regu- 
larity of  size  of  the  insects,  the  presence  or  absence 
of  foreign  materials,  the  dust,  dampness,  etc.,  are  also 
considered.  A  cochineal  is  said  to  be  greasy  when  it 
sticks  to  the  hands. 

Several  processes  have  been  proposed  for  testing 
the  value  of  cochineal.  Thus  Robiquet  made  a  com- 
parative test  by  decolorizing  with  chlorine,  the  decoc- 
tion of  the  cochineal  to  be  tried,  and  that  of  a  standard 
article.  Letellier  based  his  method  upon  the  differ- 
ence of  intensity  in  the  coloration  of  two  decoctions 
made  with  alum,  one  of  the  sample  to  be  tested,  and 
the  other  of  a  standard  cochineal.  Mr.  Anthon  has 
proposed  to  ascertain  directly  the  proportion  of  car- 
mine in  a  sample,  by  decolorizing  the  decoction  with 
a  solution  of  alum  saturated  with  ammonia.  Lastly, 
Mr.  Oscar  Koechlin  decolorizes  a  decoction  of  cochi- 
neal by  chlorine,  and  checks  the  operation  by  another 
test  with  a  solution  of  alum  saturated  with  ammonia. 
None  of  these  processes  is,  however,  sufficiently  cer- 
tain and  accurate. 

The  carmine  of  cochineal  which  is  employed  espe- 
cially for  water-color  and  miniature  painting,  for  the 
manufacture  of  artificial  flowers,  etc.,  is  the  most 
magnificent  red  color  we  possess.  Many  processes 
have  been  tried  for  obtaining  the  carmine  in  a  state 


RED  COLORS.  489 

of  purity.  Alum,  cream  tartar,  solution  of  tin,  caus- 
tic potassa,  and  the  carbonate,  nitrate,  and  binoxalate 
of  that  base,  etc.,  fiave  been  employed.  But  this 
operation  is  always  extremely  delicate,  and  requires, 
to  be  successful,  a  great  practice,  many  precautions, 
pure  water,  perfectly  clean  vessels,  and  an  intelligent 
choice  of  raw  material.  We  shall  describe  several  of 
these  processes. 

A  very  great  variety  of  carmines  are  found  in  the 
market,  and  their  tone  or  hue  is  due  to  the  process, 
or  to  more  or  less  care  taken  in  the  preparation. 

1.  Process  of  the  old  French  Encyclopedia, 

"  Take  20  grammes  of  cochineal,  2  grammes  of 
chuan'^  seeds,  70  grammes  of  the  bark  of  autow^f  and 
1  gramme  of  Roman  alum.  Pulverize  each  of  these 
substances  separately  in  a  clean  mortar.  Boil  2.33 
litres  of  pure  and  clean  water  in  a  clean  vessel,  then 
add  the  chuan,  and  give  it  three  boils.  The  liquor  is 
constantly  stirred  with  a  wooden  spatula.  Filter  the 
liquor  through  a  white  cloth  into  another  clean  vessel 
and  boil.  At  the  beginning  of  the  ebullition,  in- 
troduce the  cochineal  and  give  three  boils,  then  the 
autour  and  another  boil.  Lastly,  the  alum  is  added, 
and  the  vessel  is  removed  from  the  fire.  Filter  the 
liquor  without  pressing  the  cloth,  and  receive  it  into 
a  clean  porcelain  vessel.  After  standing  for  seven  or 
eight  days,  the  clear  liquor  is  removed,  and  the  de- 

*  Chuan  is  a  yellowish-green  seed  of  a  plant  coming  from  the 
East,  and  which  Devaux  recognized  as  the  anabasis  tamariscifoUa 
of  Linnfeus. 

f  Autour  is  a  light  and  spongy  bark  of  a  pale  cinnamon  color, 
w^hich  comes  from  the  East.  The  tree  which  produces  it  is  still 
unknown. 


490 


MANUFACTURE  OF  COLORS. 


posit  is  allowed  to  dry  in  the  sun  or  in  a  stove-room. 
The  precipitate  is  then  collected  with  a  brush  or  a 
feather,  and  is  a  finely  comminuted  and  colored  car- 
mine." 

It  should  be  remembered  that  carmine  cannot  be 
made  in  cold  weather,  because  it  does  not  settle,  and 
forms  a  jelly  which  becomes  decomposed. 

The  cochineal  left  in  the  cloth  may  be  boiled  again 
for  a  carmine  of  second  quality.  A  small  proportion 
of  annotto  is  sometimes  added  to  the  chuan  and 
autour. 

2.  Ordinary  Process, 

1  kilogramme  of  cochineal  is  dissolved,  at  a  mode- 
rate temperature,  in  20  litres  of  water  holding  30 
grammes  of  carbonate  of  potassa.  After  a  few  min- 
utes of  ebullition,  the  vessel  is  removed  from  the  fire, 
and  60  grammes  of  powdered  alum  are  dissolved  in 
the  liquor.  The  latter,  which  was  of  a  deep  red  color, 
becomes  carmine  red,  and  is  put  aside  until  the  cochi- 
neal has  settled.  The  clear  liquor  is  then  decanted  into 
another  vessel,  and  is  mixed  with  a  solution  of  isin- 
glass, passed  through  a  sieve.  The  vessel  is  heated,  and 
the  carmine  rises  to  the  surface  during  the  ebullition. 
The  liquor  is  then  removed  from  the  fire,  stirred,  and 
allowed  to  settle  for  fifteen  or  twenty  minutes.  The 
deposit  of  carmine  is  drained  upon  a  close  linen  cloth 
and  dried.  The  remaining  liquor  is  red,  and  is  used 
for  the  manufacture  of  carmine  lake. 

3.  Chinese  Process. 

The  Chinese  prepare  the  cochineal  carmine  by 
boiling  625  grammes  of  cochineal  and  3  or  4  grammes 
of  alum  in  15  to  20  litres  of  pure  river  water.  After 


RED  COLORS. 


a  few  minutes  of  ebullition,  the  vessel  is  removed 
from  the  fire,  and  the  liquor  is  left  to  settle,  and  then 
filtered.  The  precipitation  takes  place  by  pouring  in, 
drop  by  drop,  a  solution  of  tin  made  with  320  grammes 
of  ordinary  tin  salt,  500  grammes  of  nitric  acid,  and 
120  grammes  of  granulated  Malacca  tin.  The  pre- 
cipitate of  carmine  is  separated  by  decantation,  and 
is  received  upon  a  filter,  and  dried  in  a  dark  place. 

4.  German  Process. 

The  cochineal  is  boiled  in  alum-water.  After  boil- 
ing for  some  time,  more  powdered  alum  is  added,  and 
the  boiling  continued.  The  liquor  is  then  removed 
from  the  fire,  decanted,  filtered,  and  allowed  to  remain 
in  porcelain  vessels,  in  which  the  carmine  precipitates 
slowly.  After  three  days,  the  deposit  is  collected 
and  dried.  The  mother  liquors  are  preserved,  and 
give  another  quantity  of  carmine,  which  is  inferior  to 
the  first. 

5.  Process  by  Cream  Tartar. 

Put  cream  tartar  (bitartrate  of  potassa)  in  the  water 
where  cochineal  is  being  boiled,  and  after  boiling  for 
some  time  add  powdered  alum.  After  a  short  boil, 
remove  from  the  fire,  filter,  and  the  carmine  becomes 
deposited. 

6.  Process  with  Wool,  and  Formation  of  a  Lake. 

Take  250  grammes  of  cochineal,  1  kilogramme  of 
alum,  250  grammes  of  cream  tartar,  and  250  grammes 
of  wheat  bran.  All  these  substances  are  ground,  and 
thrown  into  20  litres  of  boiling  water;  250  grammes 
of  white  wool  are  then  put  in,  which  absorbs  the  car- 
mine.   The  wool  is  removed,  drained,  and  immersed. 


492  MANUFACTURE  OF  COLORS. 


still  wet,  into  a  solution  of  caustic  potassa  which  takes 
up  the  coloring  matter.  The  latter  is  precipitated 
by  a  solution  of  alum. 

T.  Wood  Process. 

Mr.  Wood  has  recently  proposed  another  mode  of 
preparation,  which  appears  to  possess  real  advantages. 
The  carmine  is  of  a  magnificent  color,  and  is  said  not 
to  change  by  time  or  by  exposure  to  the  air. 

250  grammes  of  pure  carbonate  of  soda,  and  225 
grammes  of  citric  acid,  are  dissolved  in  30  litres  of 
water.  "When  the  whole  is  boiling,  680  grammes  of 
powdered  cochineal  are  aided,  and  the  ebullition  is 
continued  for  1  or  1.5  hour.  The  liquor  is  filtered 
and  allowed  to  cool  ofi* ;  and  when  it  has  become  clear, 
it  is  boiled  again  for  5  minutes  with  250  grammes  of 
alum.  After  a  second  filtration,  it  is  allowed  to  stand 
for  two  or  three  days.  The  clear  liquor  is  then  care- 
fully decanted  from  the  deposit,  which  is  washed  with 
cold  distilled  water,  and  dried  at  a  low  temperature 
in  a  stove-room.  The  impalpable  powder  thus  pro- 
duced is,  if  desired,  mixed  with  water  rendered  alka- 
line by  ammonia,  and  mucilaginous  by  gum  Arabic. 
By  evaporation,  the  product  may  be  moulded  into 
small  blocks. 

This  carmine  may  acquire  a  peculiar  red  lustre,  by 
being  mixed  with  250  grammes  of  alum  and  a  few 
decigrammes  of  a  tin  salt ;  for  instance,  the  sulphate, 
the  nitrate  of  protoxide,  or  the  chloride  of  this  metal. 

8.  Grelley  Process. 

Mr.  Grelley  has  proposed  a  method  of  treating 
cochineal,  which  allows  of  the  almost  entire  soliltion 


RED  COLORS. 


493 


of  its  coloring  principle,  and  of  the  preparation  of  very 
handsome  red  lakes. 

First,  the  ground  cochineal  is  digested  for  four  or  five 
hours  in  water  slightly  acidulated  with  hydrochloric 
or  sulphuric  acid.  Second,  the  acid  is  saturated  with 
an  excess  of  ammonia,  and  the  latter  is  left  to  act  for 
ten  to  twelve  hours.  Third,  the  solution  is  decanted, 
and  the  deposit  is  pressed,  so  as  to  lose  no  liquor. 
Fourth,  the  excess  of  ammonia  is  saturated  with  one 
of  the  above  indicated  acids,  which  is  diluted  with  four 
or  five  times  its  weight  of  water.  Fifth,  the  useless 
precipitate  formed  by  the  last  treatment,  is  separated 
by  means  of  flannel  filters.  These  solutions  give 
immediately  a  fine  ponceau  red  lake,  when  they  are 
precipitated  by  a  mixture  (half  and  half)  of  the  two 
chlorides  of  tin,  mixed  with  a  small  quantity  of  water. 

The  aluminous  lakes  are  prepared  by  treating  these 
solutions,  first,  by  alum,  and  then  by  a  caustic  or  car- 
bonated alkali. 

This  process  is  equally  good  for  fresh  cochineal, 
and  for  that  which  has  been  already  boiled. 

§  27.  Carmine  lake,    Paris  lake.    Vienna  lake. 

Carmine  lake  is  prepared  with  the  mother  liquors 
from  which  the  pure  carmine  has  been  extracted,  and 
which  still  contain  a  great  deal  of  color.  A  solution 
of  alum  is  added,  or  a  certain  proportion  of  recently 
precipitated  alumina  is  stirred  in,  and  the  color  is 
brightened  with  a  small  quantity  of  protochloride  of 
tin.  The  precipitate  is  washed,  moulded  into  troches, 
and  dried. 

The  lake  is  the  finer  as  less  alum  or  alumina  is  em- 
ployed;  and  it  is  quite  customary,  for  the  inferior 


494  MANUFACTURE  OF  COLORS. 


qualities,  to  give  them  more  body  by  an  addition  of 
starch. 

The  finest  kinds  of  lakes  are  prepared  from  fresh 
cochineal,  which  has  not  been  previously  boiled.  20 
parts  of  powdered  cochineal  are  boiled  in  400  parts 
of  water,  holding  in  solution  10  parts  of  cream  tartar. 
The  liquor  is  filtered,  and  is  mixed  with  a  solution  of 
300  parts  of  alum,  and  a  very  small  quantity  of  pro- 
tochloride  of  tin.  The  precipitate,  which  deposits 
after  a  little  while,  is  very  bright,  and  is  collected. 
A  solution  of  carbonate  of  potassa  is  then  slowly 
added  to  the  liquor,  which  is  kept  stirred  all  the  time. 
The  new  precipitate  formed  is  thrown  upon  a  filter, 
washed,  and  dried. 

In  this  manner,  a  first  and  very  handsome  lake  is 
obtained,  and  those  which  follow  are  made  more  or 
less  rich  in  color,  by  adding  more  or  less  of  the  solu- 
tion of  alkaline  carbonate. 

§  28.  Ammoniacal  cocMneaL 

Caustic  and  concentrated  ammonia  dissolves  the 
carmine  of  cochineal,  and,  at  the  same  time,  increases 
the  brightness  of  the  color.  This  property  has  been 
made  use  of  for  preparing  what  is  called  ammoniacal 
cochineal,  and  which  is  sold  in  paste  or  in  cakes. 
One  part  of  carmine  is  dissolved  in  6  parts  of  com- 
mercial aqua  ammonia,  kept  in  a  well  stoppered 
glass  bottle.  After  several  days  of  exposure  to 
the  sun,  and  with  frequent  shakings,  the  ammonia 
has  dissolved  the  carmine.  The  liquor  is  then 
filtered,  and  precipitated  with  acid  and  alcohol.  The 
resulting  carmine  is  washed  with  dilute  alcohol  and 
dried. 


RED  COLORS. 


495 


§  29.  Bed  and  violets  from  archil, 

A  great  many  researches  and  articles  on  archil 
have  been  published ;  but  we  do  not  recognize  in  them 
the  exactness  required  by  modern  chemistry.  We 
shall  therefore  confine  ourselves  to  a  recent  article 
by  M.  H.  Gaul  tier  de  Claubry,  where  the  preparation 
of  this  coloring  substance  is  better  understood  and 
explained. 

The  remarkable  discovery  of  orcin  by  Robiquet 
demonstrated  the  presence,  in  certain  lichens,  of  a 
colorless  substance,  which,  under  the  combined  action 
of  air  and  ammonia,  is  transformed  into  a  fine  violet 
color.  So  is  indigo,  which  is  colorless  in  the  plant, 
but  becomes  blue  by  contact  with  the  air.  Several 
natural  products  extracted  from  lichens,  lecanoric 
acid  for  instance,  result,  under  certain  circumstances, 
in  orcin,  which  may  be  a  derived  product.  These 
lichens  are  treated  for  obtaining  archil,  and  this  color 
is  always  produced  under  the  combined  action  of 
air,  ammonia,  and  water.  Urine  has,  for  a  long  time, 
been  used  for  that  purpose,  and  Cocq  proposed  to 
substitute  for  it  ammonia,  which  has  already  been 
employed  in  Germany,  as  seen  by  a  memoir  of 
Hermbstaedt  (Magazin  far  Farher^  I.  290).  There 
are  several  reagents  which  will  extract  from  lichens 
the  substances  which  are  transformed  into  orcin ; 
for  instance,  water,  alcohol,  and  alkaline  solutions. 
Notwithstanding  the  great  number  of  researches 
published  on  the  subject,  it  is  impossible  to  decide 
with  certainty  upon  the  state  in  which  these  sub- 
stances exist  in  the  plants.  Moreover,  the  latter  pre- 
sent great  differences  in  their  nature  and  in  their 
origin. 


496 


MANUFACTURE  OF  COLORS. 


The  product  known  under  the  name  of  archil  is  not 
a  single  colored  substance,  but  a  compound  of  several. 
Although  similar  in  color,  they  vary  in  their  resist- 
ance to  the  action  of  certain  agents,  and,  according 
to  their  relative  proportions,  they  give  to  the  com- 
pound peculiar  qualities  for  dyeing. 

The  archil-lichens  give  at  most  10  to  12  per  cent, 
of  available  products.  If  these  be  separated  from 
the  mass  of  the  plant,  and  then  submitted  alone  to 
the  influence  of  the  air  and  of  the  ammonia,  the  tinc- 
torial product  is  obtained  under  conditions  much  more 
favorable  than  by  the  ordinary  processes. 

During  his  researches  upon  these  lichens,  Sten- 
house  employed  lime  instead  of  ammonia,  as  Heeren 
did,  for  extracting  the  color  producing  substances. 
This  process  may  be  applied ;  but,  according  to  the 
mode  of  operation,  the  results  may  be  entirely  at 
variance.  It  is  sufficient,  says  Stenhouse,  to  cut  the 
lichens  and  to  macerate  them  in  a  milk  of  lime,  and 
then  to  saturate  the  solution  by  hydrochloric  or  acetic 
acid.  All  the  available  coloring  product  will  thus  be 
obtained,  and  after  a  further  treatment  by  air  and 
ammonia,  it  will  be  transformed  into  archil.  The 
promised  result  is  indeed  obtained,  but  only  under 
given  circumstances,  that  is,  if  the  maceration  be 
very  short,  as  we  shall  prove  further  on.  The  word 
maceration,  unless  accompanied  by  the  length  of  time 
the  substance  and  the  liquid  should  be  in  contact,  is 
entirely  too  uncertain,  as  upon  it  depends  the  success 
or  failure  of  the  operation.  A  maceration  is  gener- 
ally a  long  operation,  lasting  one,  two,  or  several 
dozens  of  hours,  and  it  is  therefore  necessary  to  de- 
termine accurately  all  of  the  conditions  necessary  to 
arrive  at  a  given  result. 


RED  COLOHS. 


497 


Whatever  be  the  time  of  contact  of  the  lime  with  the 
coloring  principles,  the  latter  will  be  dissolved,  and 
one  of  two  cases  will  be  presented :  Either  an  acid  will 
precipitate  the  whole  coloring  matter  under  a  small 
volume,  which  will  then  be  transformed  into  archil 
by  treatment  with  ammonia  ;  or  the  acid  will  produce 
no  precipitate,  and  the  coloring  matter  will  remain 
entirely  in  solution.  In  the  latter  case,  evidently  all 
of  the  advantages  of  the  treatment  by  lime  disappear. 
The  following  experiments  demonstrate  these  results 
completely.  100  grammes  of  Madagascar  lichens 
were  immersed  in  600  grammes  of  a  milk  of  lime, 
holding  30  grammes  of  lime.  After  the  periods  of 
time  indicated,  the  insoluble  parts  were  separated  upon 
a  hair  sieve,  and  washed.  The  liquors  were  treated 
by  hydrochloric  acid  in  excess.  Each  precipitate 
was  collected  upon  a  cloth,  washed,  and  dried.  The 
liquors  were  neutralized  by  ammonia,  and  concen- 
trated by  evaporation ;  afterwards  an  excess  of  am- 
monia was  added,  and  they  were  kept,  a  part  of  the 
time,  at  the  ordinary  temperature,  aiid  the  remainder 
in  a  store-room  heated  at  from  50°  to  60°  C. 


Length  of 
maceration. 

Precipitate. 

Liquors. 

15  minutes. 

12  grammes,  furnishing  a  great 
deal  of  archil. 

Scarcely  any  coloration. 

1  hour. 

12.5  grammes,  furnishing  a  great 
deal  of  archil. 

Distinct  archil  coloration. 

2  hours. 

9.3  grammes,  less  archil. 

A  bright  color. 

3  " 

8 

still  less. 

A  brighter  color. 

4  " 

4  " 

less  again. 

A  still  brighter  color. 

6  " 

2.7  " 

less. 

A  richer  color. 

8  " 

2 

very  little. 

Fine  archil. 

12  " 

1.1 

scarcely  any. 

((  (( 

24  " 

0.5  " 

scarcely  any  col- 

(( u 

48  " 

.  0.5 

oration. 

U  (( 

By  repeating  the  experiment  with  double  the  pro- 
32 


498 


MAIS^UFACTUEE  OF  COLORS. 


portion  of  lime  the  precipitate  was  smaller  from  the 
second  hour,  while,  at  the  same  time,  the  liquor  con- 
tained a  great  deal  of  archil. 

These  numbers  cannot  be  given  as  absolute,  but 
they  demonstrate  in  the  most  positive  manner  that, 
by  submitting  lichens  to  the  action  of  a  milk  of  lime, 
it  is  possible,  in  accordance  with  the  mode  of  opera- 
tion, to  obtain  the  coloring  material  by  precipitation, 
or  to  leave  it  entirely  in  solution. 

"Water  alone  produces  a  similar  effect,  but  a  great 
deal  more  slowly.  A  protracted  contact  will  render 
the  coloring  products  soluble.  On  the  other  hand,  a 
very  short  contact  will  cause  a  separation. 

If,  instead  of  operating  at  the  ordinary  tempera- 
ture, the  lime  liquor  be  made  to  boil  for  three  or  four 
minutes  only,  the  addition  of  an  acid  separates  a 
brown  material,  the  color  of  which  deepens  by  contact 
with  ammonia,  but  which  furnishes  not  a  trace  of 
archil  either  at  the  ordinary  temperature  or  with  an 
increase  of  heat. 

If,  instead  of  lime,  various  soluble  salts  be  substi- 
tuted, such  as  the  phosphates  of  soda,  potassa,  or  am- 
monia, borax,  the  carbonates  of  potassa  or  soda,  etc., 
the  transformation  of  the  coloring  substances  is  very 
rapid,  and  an  ebullition  of  a  few  minutes  is  sufficient 
to  prevent  the  formation  of  any  precipitate  by  satu- 
ration with  an  acid. 

Powerful  alkalies,  such  as  potassa,  soda,  baryta, 
and  strontia,  cause  the  tranformation  more  quickly 
than  lime. 

As  I  have  previously  stated,  the  product  known 
under  the  name  of  archil  contains  several  coloring 
principles,  which  unequally  resist  the  action  of  various 
agents.    That  obtained  at  the  temperature  of  60°  C. 


RED  COLORS. 


499 


contains  the  greater  proportion  of  the  more  durable 
principles.  On  the  other  hand,  the  archil  prepared  at 
the  ordinary  temperature  contains  a  greater  or  less 
proportion  of  alterable  elements. 

For  some  time  past,  either  in  France  or  in  other 
countries,  the  manufacture  has  been  conducted  with 
the  aid  of  heat,  and  the  operation  is  more  rapid  and 
economical. 

§  30.  Percliloride  of  chromium. 

This  product,  according  to  Mr.  Wohler,  forms  a 
mass  of  red,  bright,  and  micaceous  laminse,  which 
may  be  ground  like  talc  between  the  fingers.  It  will 
be  used  as  a  coloring  substance,  especially  for  paper 
hangings,  when  it  becomes  possible  to  manufacture  it 
at  a  reasonable  price.  The  following  is  the  mode  of 
preparation : — 

Small  balls,  made  of  a  mixture  of  oxide  of  chro- 
mium, charcoal,  and  flour  paste,  are  brought  to  a  high 
temperature  in  a  covered  crucible,  and  then  put  into 
an  apparatus  composed  of  a  large  crucible,  standing 
upon  the  grate  of  an  air  furnace,  and  which  con- 
nects with  a  chlorine  generator  by  means  of  a  porcelain 
tube,  which  is  luted  on  to  a  hole  made  in  its  bottom, 
and  which  passes  through  the  grate.  The  upper  part 
of  the  tube  does  not  project  much  inside  of  the  large 
crucible,  and  is  loosely  covered  with  a  small  inverted 
crucible,  so  as  to  prevent  the  balls  from  falling  in. 
A  second  large  crucible  is  inverted  and  luted  to  the 
first,  and  has  also  a  small  hole  in  its  bottom  for  the 
escape  of  the  gases. 

As  soon  as  the  apparatus  is  filled  with  gaseous 
chlorine,  the  lower  crucible  is  raised  to  an  intense  heat, 
and  the  fire  is  so  conducted  that  the  sublimed  perchlo- 


500 


MANUFACTURE  OF  COLOnfe. 


ride  of  chromium  condenses  in  the  upper  crucible, 
the  temperature  of  which  is  not  above  a  dark  red  heat. 
As  the  perchloride  of  chromium,  heated  in  contact 
with  the  air,  is  decomposed,  it  is  necessary  to  continue 
the  passage  of  chlorine  during  the  cooling  of  the  ap- 
paratus. The  operation  should  be  conducted  in  the 
open  air,  or  under  a  chimney  with  a  good  draft.  The 
perchloride  is  then  washed  with  water,  to  remove  the 
chloride  of  aluminium  resulting  from  the  clay  of  the 
crucible.  If  the  flow  of  chlorine  has  been  weak,  the 
product  will  contain  a  certain  quantity  of  simple 
chloride,  which,  during  the  washings,  causes  the  solu- 
tion of  a  portion  of  the  perchloride,  which  is  thus  lost. 

§  31.  CJirome  red. 

We  have  already  described  the  manufacture  of  this 
fine  product,  when  speaking  of  the  preparation  of 
chrome  yellow,  by  the  process  of  Mr.  Habich. 

SECTION  Y. 

BROWN  AND  BLACK  COLORS. 
1.  BROWNS. 

§  1.  Mars  hrowns. 

While  examining  the  preparation  of  ochres,  we  have 
seen  that,  by  calcining  a  Mars  yellow  at  various  tem- 
peratures, and  under  peculiar  conditions,  this  sub- 
stance passes  through  a  series  of  colors  and  hues, 
among  which  there  is  a  brown  of  sesquioxide  of  iron 
which  is  very  durable,  but  somewhat  expensive. 

We  shall  here  indicate  a  process  due  to  Mr.  Salve- 
tat,,  by  which  it  is  possible  to  obtain  a  brown,  and 
also  a  red  ochre  of  great  brightness. 

A  solution  is  made  in  hydrochloric  acid,  of  280 


BROWN  COLORS. 


501 


grammes  of  metallic  iron,  and  330  grammes  of  zinc. 
The  whole  is  afterwards  precipitated  by  the  carbonate 
of  soda,  and  the  precipitate  is  carefully  washed,  in 
order  to  remove  all  the  chloride  of  sodium  or  car- 
bonate of  soda.  The  deposit,  which  is  green  at  the 
beginning,  becomes  brown ;  and,  when  all  greenish 
hue  has  disappeared,  it  is  drained  upon  sheets  of  fil- 
tering paper  spread  upon  cloths.  Lastly,  the  dried 
product  is  brought  to  the  desired  hue  by  calcination 
upon  clay  dishes. 

The  zinc  and  iron  may  be  replaced  by  the  sulphates 
of  these  metals,  provided  their  composition  be  taken 
into  account. 

The  tone  or  hue  of  the  pigment  is  modified  by  mix- 
ing 1,  2,  3,  .  .  .  equivalent  weights  of  zinc,  with  2,  4, 
6,  .  .  .  equivalents  of  iron.  The  addition  of  nickel, 
cobalt,  or  manganese  produces  darker  hues,  resembling 
wood,  sepia,  etc. 

§  2.  Iron  minium. 

MM.  Bouchard  and  Clavel  have  made  many  expe- 
riments for  doing  away  with  red  lead  in  painting  and 
in  the  manufacture  of  mastics,  and  they  have  taken 
as  a  substitute  a  Burgundy  ochre. 

Since  then,  they  have  taken  out  a  patent  for  a  new 
product  which  fhey  call  ferrugine  alumineuse,  which 
replaces  red  lead  very  advantageously  as  regards 
economy,  and  presents  none  of  the  inconveniences  of 
the  lead  product. 

A  new  color,  preventive  of  rust,  and  which  may 
enter  into  the  composition  of  cements,  has  recently 
been  manufactured.  It  is  iron  minium,  which  seems 
intended  to  take  the  place  of  red  lead  in  iron  and 
wood  painting.  "We  borrow  from  the  Oenie  Indus- 
triel  the  following  paragraphs  : — 


502 


MANUFACTURE  OF  COLORS. 


"  The  new  product  possesses  all  the  qualities  of 
red  lead,  without  any  of  its  inconveniences.  It  is  of 
a  fine  brown  color,  constant  in  price,  and  mixes  per- 
fectly well  with  linseed  oil.  Under  equal  volumes, 
it  covers  more  than  red  lead,  and  is  a  better  protection 
against  oxidization. 

"  Iron  minium  is  a  very  pure  substance,  into  the 
composition  of  which  no  acid  enters,  nor  any  other 
combination  hurtful  to  the  painted  articles.  In  fact, 
according  to  Mr.  Loppens,  professor  at  the  Industrial 
School  of  Ghent,  it  is  a  composition  which  cannot  be 
altered  by  any  of  the  causes  generally  acting  upon 
red  lead,  and  which  may  replace  the  latter  in  all  its 
uses. 

"  Three  different  analyses  of  iron  minium  gave — 


I.  Water  1.3 

Clay  25.T 

Ked  lead=*^  3.2 

Carbonate  of  lime  0.6 

Peroxide  of  iron     .       .       .       .       .  .67.7 

Loss        ........  L5 


100.0 

IL  Silica   0.105 

Alumina   0.035 

Peroxide  of  iron   0.820 

Lime  •  .       .  0.020 

Water   0.010 

Magnesia   0.010 


1.000 

III.  Peroxide  of  iron  68.95 

Aluminous  earth  (clay)  ....  1.48 
Burnt  clay  29.57 


100.00 


*  This  red  lead  comes  from  the  litharge  employed  as  a  dryer. 


BROWN"  COLORS. 


503 


"  After  experiments  on  painting,  made  under  the 
direction  of  Dutch  engineers,  in  comparison  with  red 
lead,  the  comparative  weights  were — 


"And  the  specific  gravities,  by  hydrostatic  pro- 


"  The  analyses  prove  the  absence  of  any  kind  of 
acid,  which,  even  in  the  smallest  proportion,  alters  the 
colors,  especially  when  it  is  sulphuric  or  hydrochloric 
acid. 

"  A  comparison  of  these  analyses  with  those  made 
of  Oriental  hrown,  Burgundy  red^  caput  mortum^  or 
colcothar,  shows  the  great  superiority  of  iron  minium. 

"  Colcothar  always  retains  a  trace  of  sulphuric  acid. 
Indeed,  it  is  the  residue  of  the  manufacture  of  the 
l!^ordhausen  sulphuric  acid,  which  is  prepared  by  the 
distillation  of  sulphate  of  iron.  Iron,  coated  with  this 
pigment,  is  rusted,  instead  of  being  preserved. 

"  Employment  of  iron  minium, — We  know  that  red 
lead  is  simply  mixed  with  raw  or  boiled  linseed  oil, 
and  that  the  mixture  dries  so  rapidly  that  it  should 
be  prepared  only  a  short  time  before  its  use.  More- 
over, its  manipulation  is  unhealthy,  and  may  occasion 
lead  colic,  the  same  as  white  lead. 

"  The  preparation  of  iron  minium  for  painting  is 
quite  like  that  of  red  lead,  that  is,  it  is  simply  mixed 
with  raw  or  boiled  linseed  oil.  If  thin  coats  are  de- 
sired, the  mixture  is  ground,  and  a  little  litharge 
dryer  is  added,  preferably  to  essence  of  turpentine 
which,  as  a  general  rule,  does  not  improve  colors. 


Red  lead 
Iron  minium 


1.4T 
3.13 


cess  at  22°  C— 


Iron  minium 
Red  lead 


3.Y4 
8.24 


504  MANUFACTUKE  OF  COLORS. 


"  In  painting  the  hulls  of  ships,  red  lead  is  mixed 
with  a  certain  proj)ortion  of  bisulphate  of  mercury, 
which  is  a  virulent  poison,  and  is  intended  to  destroy 
molluscs  and  wood  boring  insects.  This  poison  may 
be  incorporated  with  iron  minium,  which  is  not  there- 
by altered. 

"Mixed  with  one-third  of  white  lead,  iron  minium 
forms  an  excellent  mastic,  similar  to  that  made  with 
red  lead,  and  which  is  much  cheaper,  and  becomes 
very  hard  after  drying  for  some  time. 

"As  the  paint  made  with  iron  minium  resists  a 
strong  heat,  it  may  be  advantageously  employed  for 
painting  the  interiors  of  boilers,  and  preserving  them 
from  incrustation. 

"  Mixed  in  certain  proportions  with  coal  tar,  iron 
minium  forms  a  very  firm  coat,  which  penetrates  the 
pores  of  the  wood  and  hardens  it  considerably. 

"  The  brown  color  of  iron  minium  is  not  altered  by 
the  sulphides,  while  red  lead  is,  and  remains  a  long 
time  in  its  natural  state.  It  will,  therefore,  be  found 
advantageous  and  economical  to  use  this  paint  for 
the  hulls  of  vessels  in  ports  where  the  filth  of  the  city 
is  poured  into  the  docks." 

§  3.  Van  DyJce  hrown, 

Van  Dyke  brown  is  also  a  color  derived  from  iron, 
and  is  very  durable. 

It  is  prepared  by  the  calcination  of  certain  yellow 
ochres  found  in  the  south  of  France.  The  resulting 
frit  is  sold  in  lumps,  in  grains,  or  as  an  impalpable 
powder.  Ochres,  as  we  know,  hold  alumina  and  sand, 
;  which  combine  with  the  oxide  of  iron  at  a  high  tem- 
perature. 

A  Van  Dyke  brown  is  also  manufactured  by  cal- 


BROWN  COLORS. 


505 


cining  sulphate  of  iron  several  times.  The  proper 
color  is  arrived  at  by  practice.  We  understand  that 
this  last  brown,  which  is  entirely  an  oxide  of  iron, 
and  of  a  purer  color  than  the  preceding,  is  more  ex- 
pensive. It  is  often  adulterated  with  the  brown  frit, 
and  the  fraud  is  detected  by  means  of  concentrated 
and  hot  acids,  which  easily  dissolve  the  pure  oxide  of 
iron,  and  with  difficulty  the  ochre  brown. 

By  mixing  Van  Dyke  brown  with  variable  pro- 
portions of  red  ochre  and  binoxide  of  manganese,  very 
durable  browns  are  obtained,  which  do  not  require 
dryers  when  they  are  used  hot. 

Other  durable  browns  may  also  be  prepared  by 
mixing  this  pigment  with  lamp  or  ivory  black. 

§  4.  Manganese  hrown, 

Mr.  J.  Lefort,  in  his  Ghimie  des  Couleurs^  states  that 
the  analyses  of  old  Roman  paintings  show  that  the 
oxide  of  manganese  was  employed  as  a  brown  pig- 
ment. This  chemist  has,  therefore,  made  a  few  ex- 
periments by  which  he  has  ascertained  that  the  bin- 
oxide  of  manganese  ground  in  oil,  gives  a  very  hand- 
some and  durable  paint.  He  proposes  to  manufacture 
this  color  as  follows  : — 

"  The  protochloride  of  manganese  resulting  from  ^ 
the  manufacture  of  chlorine,  or  the  protosulphate 
obtained  by  the  calcination  of  the  protoxide  of  man- 
ganese with  sulphate  of  iron,  is  dissolved  in  water  at 
the  temperature  of  30°  to  40°  C.  Then  a  solution  of 
hypochlorite  of  soda  (Labarraque's  liquor),  or  one  of 
hypochlorite  of  potassa  ( Javelle's  water),  holding  a 
certain  quantity  of  carbonate  of  soda,  is  added  until 
the  precipitate  formed  does  not  change  color.  "When 
the  oxidization  is  complete,  the  liquors  are  decanted 


506 


MANUFACTURE  OF  COLORS. 


and  the  precipitate  is  washed  first  with  water  holding 
of  sulphuric  acid,  and  then  with  pure  water  until 
the  rinsings  are  tasteless.  The  binoxide  of  man- 
ganese, after  being  dried  in  a  stove-room,  is  an  im- 
palpable and  dark-brown  powder,  which  covers  well 
and  is  entirely  innocuous." 

§  5.  Brown  of  manganate  of  lead. 

Take  1  part  of  oxide  of  manganese,  1  of  oxide  of 
lead,  and  1  part  of  sulphate  of  ammonia,  and  mix  the 
whole  with  peat,  so  as  to  form  a  paste  which  is  dried 
and  burned.  The  resulting  pearl-gray  compound  is 
then  mixed  with  1  part  of  nitrate  of  lead  and  1  part 
of  sulphate  of  iron,  and  the  product  (after  calcina- 
tion ?)  is  said  to  be  a  fine  sienna  earth. 

§  6.  Prussian  hrown, 

Mr.  Bouvier  has  indicated  a  process  for  preparing 
this  brown,  which  was  discovered  by  the  painter 
Toeffer. 

"Heat  an  iron  ladle  upon  a  brisk  fire  until  it  be- 
comes red,  and  then  throw  into  it  pieces  of  Prussian 
blue  of  the  size  of  a  filbert.  Each  piece  will  soon 
split,  scale  off*,  and  become  red.  Then  remove  the 
ladle  from  the  fire  and  let  it  cool.  A  longer  heating 
will  destroy  the  desired  color.  When  the  pieces  are 
broken,  there  are  seen  black  parts  mixed  with  others 
of  a  yellowish-brown  color,  which  is  the  proof  of  a 
good  preparation.  Grind  the  whole  together,  and 
there  will  be  produced  a  brown  resembling  bistre  or 
a  very  clear  asphaltum." 

This  process  would  be  improved  by  calcining  in  a 
closed  vessel.  The  product  would  be  more  homo- 
geneous, and  the  temperature  more  easily  regulated 


BROWN  COLORS. 


507 


for  a  given  tone  of  color.  This  pigment  is  very  dur- 
able and  covers  well. 

§  7.  Bed-brown. 

We  have  described  the  preparation  of  this  color  in 
Section  IV.,  §  5,  and  we  have  seen  that  it  is  a  mixture 
of  oxide  of  iron  and  litharge,  or  red  lead,  which  is 
fused  in  a  crucible. 

§  8.  Grilt-brown, 

This  brown  is  a  binoxide  of  lead,  and  is  prepared 
as  follows : — 

Orange  mineral,  litharge  or  red  lead,  is  very  finely 
powdered,  and  heated  in  a  vessel  with  Javelle  water 
or  chloride  of  sodium  (hypochlorite  of  soda  ?),  added 
by  small  quantities  at  a  time.  The  material  becomes 
gradually  brown,  and  when  the  desired  tone  of  color 
has  been  obtained,  it  is  washed  and  dried. 

Mr.  Lefort  asserts  that  the  product  is  of  a  finer 
quality  when  white  lead  is  employed. 

§  9.  Chicory -brown, 

"When  certain  vegetable  substances  are  burned  in 
closed  vessels,  the  root  of  chicory  for  instance,  there 
is  obtained  a  fine  powder  which,  after  boiling  in 
water,  gives  a  colored  solution.  If  the  latter  be 
evaporated  to  dryness,  the  residue  is  a  brown  sub- 
stance, soluble  in  water,  and  w^hich  is  employed  in 
water-color  painting.  The  color  is  rich,  but  not 
durable. 

§  10.  JJlmin-brown, 

Dumenil  recommends  as  a  color  for  miniature  paint- 
ing, the  brown  deposit  formed  by  the  action  of  cans- 


508  MANUFACTURE  OF  COLORS. 


tic  potassa  upon  alcohol.  Fused  caustic  potassa, 
coarsely  broken,  is  digested  with  twice  its  weight  of 
alcohol,  and  then  filtered  through  a  cloth. 

The  liquor  is  heated  for  a  few  hours,  becomes  dark- 
brown,  and  deposits  a  dull-looking  powder,  which  is 
collected  upon  a  filter  and  washed  with  water  acidu- 
lated by  hydrochloric  acid. 

By  melting  in  a  copper  vessel,  three  parts  of  sugar 
with  one  of  potassa,  until  the  mixture  becomes  a  dark 
brown,  and  then  dissolving  in  water,  filtering,  and 
precipitating  with  an  excess  of  hydrochloric  acid, 
there  is  produced  a  brown  color,  which  is,  however, 
inferior  to  the  preceding  one. 

This  color  may  also  be  obtained  by  treating  peat, 
cotton,  lignites,  etc.,  by  alkalies ;  starch,  flour,  etc., 
by  concentrated  acids ;  or  wood-soot,  bistre,  etc.,  by 
caustic  potassa. 

Ulmin-brown  is  a  fine  color,  which  mixes  well  with 
other  pigments,  and  flows  well  under  the  brush. 

§  11.  Bistre. 

This  water  color  is  prepared  from  the  soot  which 
accumulates  in  the  flues  of  fireplaces  in  which  wood 
is  burned.  Its  preparation  for  becoming  a  pigment 
is  as  follows  : — 

The  brightest  and  darkest  fragments  of  soot,  result- 
ing from  the  combustion  of  beech-wood,  are  powdered 
and  passed  through  a  silk  sieve.  The  powder  is 
stirred  in  hot  water  for  twenty-four  hours,  and  again 
in  another  water.  All  the  liquors  are  collected  and 
allowed  to  settle.  The  precipitate  is  then  mixed  with 
gum- water,  and  evaporated  in  a  stove-room  to  the 
consistency  of  a  solid  extract. 


BROWI^"  COLOES. 


509 


§  12.  Bitumens  or  Asphaltum, 

Such  are  the  names  given  to  various  liquid  or  solid 
substances,  which  melt  at  a  moderate  temperature, 
and  have  a  more  or  less  pungent  and  peculiar  smell. 
They  are  very  combustible,  and  leave  a  small  charred 
residue,  which  is  very  light  and  easily  reduced  to 
ashes.  The  hitumen  naphtha  is  abundant  in  Persia, 
upon  the  shores  of  the  Caspian  Sea,  near  Bakou,  etc. 
It  oozes  constantly  from  the  soil,  and  is  accompanied 
by  hydrocarbon  gases,  which  are  burned  by  the  in- 
habitants for  various  purposes.  This  bitumen  is  also 
found  in  Calabria,  in  Sicily,  in  America,  etc. 

Bitumen  ofJudea  or  Asphaltum. — This  is  the  kind 
most  generally  used  in  painting,  and  it  is  found  on 
the  surface  of  the  Dead  Sea.  It  has  also  been  found, 
under  ground,  in  America,  China,  the  island  of  Trini- 
dad, France,  Germany,  Seyssel,  Ussel,  Dax,  etc.,  and 
in  the  Carpathian  Mountains.  Asphaltum  is  black 
or  brown,  solid,  hard,  fusible,  and  breaking  with  a 
smooth  fracture.  When  pure,  it  is  insoluble  in  alco- 
hol, very  combustible,  and  leaves  a  residue  amounting 
sometimes  to  15  per  cent.  It  was  employed  by  the 
Egyptians  for  embalming  their  dead. 

Bitumen  or  Betin  asphaltum. — This  substance  is 
of  a  light-brown  color,  with  a  resinous  fracture,  very 
fusible,  and  partly  soluble  in  alcohol. 

Melted  bitumen  becomes  very  brown  and  trans- 
parent. But  as  it  destroys  the  drying  quality  of  oils, 
it  should  be  dissolved  in  essence  of  turpentine.  This 
solution,  which  can  be  made  in  the  cold  or  with  very 
little  heat,  is  so  thick,  that  in  order  to  paint  with  it, 
it  requires  to  be  mixed  with  the  emplastic  oil  of  the 
Italians  and  with  a  mastic  varnish. 


510 


MAKUrACTURE  OF  COLORS. 


A  very  drying  bitumen  may  be  prepared  by  the 


following  process : — 

Venice  turpentine  .       .       .       .       .       .15  parts. 

Gum-lac  60  " 

Asphaltum  90  " 

Drying  linseed  oil   240  " 

White  wax  30 


The  gum  lac  is  dissolved  in  the  turpentine  by  por- 
tions at  a  time,  and  no  more  is  added  until  the  pre- 
vious addition  is  melted.  The  asphaltum  is  then 
treated  in  the  same  manner.  While  this  operation  is 
going  on,  the  linseed  oil  is  heated  nearly  to  the  boil- 
ing point,  and  afterwards  mixed  by  degrees  with  the 
melted  asphaltum.  Lastly,  the  wax  is  added  before 
cooling.  The  whole  is  poured  upon  a  stone  slab,  and 
worked  with  the  muUer  or  the  knife. 

Since  it  has  become  possible  to  employ  the  pure 
bitumen,  and  to  render  it  drying  and  easily  ground, 
Mummy  and  Van  Dyke  browns  are  much  less  em- 
ployed, because  these  latter  pigments  are  often  adul- 
terated with  other  coloring  substances. 

Bitumen  or  asphaltum  stands  the  action  of  light 
quite  well ;  but  the  tone  of  its  color,  its  durability, 
and  its  transparency  vary  with  the  nature  of  the  bitu- 
mens and  the  mode  of  preparing  them.  The  bitumens 
generally  found  in  the  trade  are  those  of  Jadea, 
Grenoble,  and  Strasbourg.  When  pure,  they  burn 
and  leave  very  little  ashes,  or  none  at  all. 

§  13.  Sepia, 

Sepia  is  furnished  by  a  marine  cephalopod,  the 
cuttle-fish  {Sepia  officivialis)^  which  is  very  common 
on  our  shores.  This  color  is  extracted  from  a  pocket 
filled  with  a  brown  liquor,  which  the  fish  emits  in 


BROWN  COLORS. 


511 


order  to  obscure  the  transparency  of  water  when  it  is 
pursued  by  its  enemies.  As  soon  as  it  has  been 
caught,  this  pocket  is  removed  and  dried  in  the  sun. 
It  is  then  powdered,  ground  with  a  concentrated 
sohition  of  carbonate  of  potassa,  and  boiled  for  some 
time.  The  solution  is  filtered,  saturated  with  an  acid, 
and  left  to  settle.  The  precipitate  is  washed  first  by 
decantation,  and  afterwards  upon  a  filter,  and  then 
di-ied.  This  pigment  forms  an  impalpable  powder  of 
a  dark-brown  color,  insoluble  in  water  or  alcohol,  and 
is  very  fine  and  durable. 

§  14.  TJmher, 

This  earth  appears  to  be  a  hydrated  silicate  of 
iron  and  manganese,  which  is  found  native,  and  was 
formerly  imported  from  the  Roman  province  of  Um- 
bria.  It  now  comes  from  the  island  of  Cyprus.  The 
natural  article  is  in  the  state  of  brown  lumps,  adher- 
ing to  the  tongue,  staining  the  flesh,  and  falling  to 
powder  in  water.  The  impurities  are  removed  by 
washing,  and  the  floated  article,  after  settling,  forms 
a  light-brown  powder,  which  is  employed  raw  or 
burnt. 

Powdered  umber,  or  that  which  has  been  calcined 
too  much,  reddens  or  blackens  by  the  dehydration 
of  the  iron  or  the  superoxidization  of  the  manganese. 
It  is  rarely  employed  alone,  and  it  mingles  well  with 
other  colors  or  with  slaked  lime. 

§  15.  Sienna  earth. 

This  is  an  earthy  substance,  exported  from  Sienna, 
in  Tuscany,  and  which  owes  its  color  to  a  hydrated 
oxide  of  iron.    It  is  used  raw  or  burnt. 

Eaw  sienna  is  a  dark-yellow  on  the  exterior,  and 


512 


MANUFACTURE  OF  COLORS. 


a  light-yellow  inside ;  its  powder  is  greenish-yellow. 
Burnt  sienna  is  either  a  light  or  dark-red  when  in 
lumps,  but  its  powder  is  of  a  dark-red  color. 

§  16.  Cologne  and  Cassel  earths. 

Cologne  earth  is  a  brown  earthy  substance,  which 
takes  fire  easily,  and  burns  without  flame  or  smoke 
like  decayed  w^ood.  It  produces  white  or  red  ashes, 
and  presents  all  the  characteristics  of  organic  mate- 
rials. It  is  found  in  the  neighborhood  of  Cologne, 
especially  at  Briihl  and  Liblar,  where  it  forms  con- 
siderable deposits,  as  much  as  12  metres  in  thickness, 
and  extending  over  several  kilometres. 

This  earth  is  smooth  to  the  touch,  crumbles  to  a 
fine  powder,  is  as  light  as  water,  and  of  a  brown- 
black  color.  The  impurities  are  separated  by  wash- 
ings, and  the  pigment  is  moulded  into  large  troches, 
which,  being  ground  in  water  or  oil,  give  a  very  dur- 
able and  fine  brown  color. 

§  17.  Puce  with  chr ornate  of  manganese. 

According  to  Mr.  Persoz,  the  calcined  chromate  of 
manganese  gives  a  handsome  puce  (flea)  color,  which 
may  be  used  for  oil  and  porcelain  painting,  and  for 
calico  printing  with  albumen. 

II.  BLACKS. 
A.  MINERAL  BLACKS. 

§  1.  Schist  or  shale  black. 

This  black  is  obtained  by  the  carbonization  of 
bituminous  schists  in  closed  vessels,  but  all  kinds  are 
not  equally  good  for  this  manufacture,  and  the  light 


BLACK  COLORS. 


513 


schists  are  generally  preferred,  the  Scotch  Bog-head 
for  instance. 

In  the  arts  the  latter  schist  is  calcined  in  large 
east-iron  retorts,  and  there  are  obtained  essential  oils 
for  lighting,  certain  gases,  and  a  carbonaceous  resi- 
due which  has  received  the  name  of  schist  black. 

By  a  slow  distillation  and  a  moderate  heat,  bog- 
head furnishes  from  35  to  40  per  cent,  of  crude  oil, 
weighing  on  an  average  850  grammes  per  litre,  that 
is  to  say,  a  sp.  gr.  =  0.850.  The  carbonaceous  resi- 
due amounts  to  about  one-half  of  the  distilled  schist, 
and  is  directly  removed  from  the  retorts  into  closed 
iron  vessels,  where  it  cools  off  without  the  contact  of 
the  air.  It  then  forms  light  and  porous  lumps,  which 
are  easily  ground. 

This  charred  mass  from  bog-head  contains  from  30 
to  35  per  cent,  of  pure  carbon,  and  from  70  to  65  per 
cent,  of  alumina  mixed  with  a  small  proportion  of 
silica,  magnesia,  lime,  and'sulphide  of  iron. 

This  material  has  been  but  recently  used  for  paint- 
ing. It  combines  readily  with  drying  oils,  and  gives 
an  intense  and  handsome  black,  which  is  at  the  same 
time  very  economical. 

§  2.  Bituminous  coal  Mack, 

Mr.  P.  T.  Laval  ley e  has  proposed  to  manufacture 
a  black  color  with  bituminous  coal  in  this  manner: — 
Two  pairs  of  ordinary  millstones  are  necessary, 
in  which  coal  is  substituted  for  wheat. 

"  Small  coal  (slack)  is  to  be  preferred,  since  it  is 
cheaper  than  the  large,  and  saves  the  expense  of 
breakage.  If,  however,  there  are  too  large  lumps, 
they  should  be  broken  with  a  hammer. 

"  After  the  coal  has  passed  through  the  first  pair 
33 


514 


MANUFACTURE  OF  COLORS. 


of  stones  it  goes  through  the  second,  the  stones  of 
which  are  one-third  nearer  each  other  than  the  first 
set. 

"The  powdered  pigment  is  then  ground  again  as 
usual  with  essence  of  turpentine,  or  linseed  oil,  or 
varnish,  according  to  the  use  it  is  intended  for.  It  is 
suitable  for  all  kinds  of  oil  painting,  for  houses,  car- 
riages, etc.  It  is  also  employed  in  distemper  painting 
with  size  and  milk." 

§  3.  Black  of  chromaie  of  copjper. 

Mr.  Persoz  has  demonstrated  that  the  basic  chro- 
mate  of  copper  contains  three  equivalents  of  oxide  of 
copper,  and  that  by  calcination  it  loses  a  portion  of 
its  oxygen,  and  is  transformed  into  an  oxide  of  copper 
soluble  in  hydrochloric  acid,  and  into  a  compound 
insoluble  in  that  acid. 

The  calcination  should  take  place  in  contact  with 
the  air,  and  not  in  a  closed  crucible,  because,  in  the 
latter  case,  the  resulting  salt  is  different  and  contains 
the  copper  in  the  protoxide  state.  This  second  com- 
pound resembles  galena,  while  the  first  is  an  amor- 
phous black  powder. 

The  pigment,  obtained  by  calcining  in  the  air  the 
basic  chromate  of  copper,  may  also  be  produced  by 
the  calcination  of  a  mixture,  in  fixed  proportions,  of 
bichromate  of  potassa  and  nitrate  of  copper.  It  is 
remarkable  for  the  intensity  of  its  black  amorphous 
color,  its  comminution,  and  its  unalterability.  It 
may  be  employed  in  oil  colors,  and  probably  also,  in 
porcelain  painting,  and  calico  printing  with  albumen. 


BLACK  COLORS. 


515 


§  4.  Ehony  hlacJc, 

It  is  said  that  a  fine  ebony  black  color  may  be 
obtained  by  burning  nitrate  of  copper  with  peat. 

B.  VEGETABLE  BLACKS. 

§  5.  PeacJi'Stone  hlack. 

This  black  is  prepared  by  calcining  in  closed 
vessels,  the  stones  of  peaches,  apricots,  and  other 
fruits.  The  calcined  stones  are  broken  in  a  cast-iron 
mortar,  and  the  powder,  after  having  passed  through 
a  silk  sieve,  is  ground  in  water.  The  color  is  hand- 
some, but  has  a  reddish  tinge.  Ground  with  oil  and 
white  lead,  the  color  called  in  England  old  gray  is 
obtained. 

§  6.  Fusain  {spindle  tree^  prickle  wood)  hlack. 

This  black  is  the  result  of  the  calcination  of  the 
prickle  wood.  The  dry  wood  is  divided  into  small 
rods,  which  are  placed  in  a  crucible  of  cast-iron  or  of 
thick  sheet-iron.  A  layer  of  sand,  from  8  to  10  cen- 
trimetres  thick,  is  placed  between  the  wood  and  the 
crucible  cover,  which  has  an  opening  for  the  escape 
of  the  gases.  The  crucible  is  then  brought  to  and 
maintained  at  a  red  heat  for  two  hours.  After  cool- 
ing, the  rods  of  charcoal  are  removed,  and  cut  in  the 
shape  of  pencils. 

It  has  been  remarked  that  the  j^oung  branches  give 
a  lighter  and  a  better  charcoal  than  the  old  wood. 

§  7.  Qrape-mne  hlack, 

Thi  s  is  the  product  of  the  carbonization  in  closed 
vessels,  of  the  clippings  of  grape-vines  at  the  prun- 


516 


MAINTUFACTURE  OF  COLORS. 


ing  time.  The  black  is  very  intense  and  light,  and 
is  ground  by  the  ordinary  process. 

§  8.  Corh  hlack. 
This  black,  also  called  Spanish  black,  is  prepared 
by  calcining  in  closed  vessels  the  waste  of  cork 
cuttings.    It  is  very  fine,  and,  combined  with  other 
pigments,  it  produces  very  handsome  hues. 

§  9.  German  hlack. 

This  black  is  very  much  employed  for  copperplate 
printing,  and  is  obtained  by  the  calcination  in  closed 
vessels,  of  a  mixture  of  grape  stalks,  dried  wine 
lees,  peach-stones,  and  bone  waste.  The  proportions 
of  these  various  substances  are  not  very  constant,  and 
a  very  fine  black  may  be  produced  from  the  following 
proportions  :  3  parts  of  unboiled  bones,  7  of  dry  stalks, 
5  of  dry  wine  lees,  and  6|  of  peach-stones  from  the 
residue  of  the  distillery.  If  the  peach-stones  have 
not  been  distilled,  5  parts  are  sufficient. 

After  cooling,  the  charcoal  is  removed  from  the 
crucible,  and  powdered  in  a  mortar.  The  powder  is 
passed  through  a  silk  sieve,  and  then  ground  in  water. 
The  paste,  brought  to  the  proper  consistency,  is 
moulded  into  lumps,  which  are  dried  in  a  stove-room, 
and  constitute  a  German  black  of  the  first  quality. 

§  10.  Frankfort  hlack, 
Frankfort  black  is  prepared  by  burning  wine  lees 
in  closed  vessels,  powdering  and  grinding  the  char- 
coal in  water,  and  then  moulding  it  into  cakes.  The 
charcoal  hlack  for  printing  is  prepared  in  the  same 
manner.  The  grinding  is  effected  between  stones 
kept  in  a  kind  of  tub,  in  the  bottom  of  which  there 
is  an  opening  for  removing  the  ground  product.  In 


BLACK  COLORS. 


517 


works  arranged  for  the  purpose,  the  motive  power, 
horse  or  steam,  is  generally  in  the  centre,  and  drives 
on  one  side  the  stamps  for  pulverizing,  and  on  the 
other  the  mills  for  grinding.  Tubs  raised  somewhat 
above  the  ground  are  placed  along  the  walls,  and 
receive  the  ground  black,  which  is  allowed  to  settle. 
After  the  decantation  of  the  liquor  above,  the  black 
is  drained  in  baskets  lined  with  cloths,  and  then 
moulded  and  dried.  The  moulds  are  8  centimetres 
in  height  and  10  in  diameter,  and  are  formed  each  of 
a  thin  wooden  ring.  Several  such  moulds  are  placed 
upon  a  board  before  being  filled  with  the  black  paste. 

These  various  kinds  of  black  are  employed  for 
painting,  for  copperplate  printing,  etc.  The  sticks 
of  fusain  are  used  for  sketching. 

§  11.  Lampblack. 

The  manufacture  of  lampblack  is  quite  an  impor- 
tant branch  of  trade  in  certain  localities.  This  black 
is  obtained  by  the  incomplete  combustion  of  sub- 
stances very  rich  in  carbon,  and  which  burn  with  a 
fuliginous  flame.  This  combustion  produces  a  black 
dust,  exceedingly  light,  which  is  known  in  the  arts 
under  the  name  of  lampblack. 

The  substances  generally  employed  are  resins,  tar, 
heavy  oils  from  tar  and  schists,  and  vegetable  oils. 
The  latter  give  the  finest  and  purest  black,  but  its 
price  is  higher. 

There  are  in  the  trade  three  principal  kinds  of 
lampblack : — 

1.  The  resin  black  ; 

2.  The  tar  black  ; 

3.  The  oil  or  lampblack. 

We  shall  describe  the  process  for  manufacturing 
each,  in  the  above  order. 


518  MANUFACTURE  OF  COLORS. 


First  Process — Resin  Black. 


As  is  indicated  by  its  name,  this  black  is  obtained 
by  tli^e  combustion  of  resins.  The  apparatus  is  com- 
posed of  a  cylindrical  building  A  (Fig.  59),  lined  in- 


side with  hanging  cloths,  upon  which  the  black  con- 
denses. This  building  is  covered  with  a  conical 
roof,  supporting  a  movable  sheet-iron  cone  b,  which 
is  perforated  at  its  summit  in  order  to  permit  of  a 
certain  draft  of  air.  This  cone,  the  lower  diameter 
of  which  is  nearly  that  of  the  building  itself,  hangs 
by  a  rope  passing  through  the  pulley  c,  and  may, 
therefore,  be  raised  or  lowered  at  will.  Lastly,  the 
apparatus  is  completed  with  the  fireplace  d,  outside 
of  the  building,  and  which  contains  a  small  cast-iron 
kettle  E,  in  which  the  resin  is  placed.  The  operation 
begins  by  heating  the  kettle  e,  filled  with  resin. 
When  the  latter  is  melted,  it  is  inflamed,  and  the  in- 
complete combustion  of  the  resinous  vapors  causes 
the  formation  of  a  quantity  of  large  black  flakes, 
which  become  attached  to  the  cloths  hanging  in  the 
room.    The  quantity  of  air  necessary  to  the  combus- 


Fig.  59. 


BLACK  COLORS. 


519 


tion  is  regulated  by  a  small  sliding  damper  on  the 
door  of  the  fireplace.  It  is  important  to  operate  with 
the  smallest  quantity  of  air  possible,  otherwise  the 
product  will  not  be  so  abundant. 

When  the  resin  held  in  the  kettle  is  burned  out, 
another  quantity  is  added,  and  the  operation  is  con- 
tinued for  several  days.  "When  the  black  has  accu- 
mulated in  the  room  to  such  an  extent  that  the  ope- 
ration cannot  be  continued,  the  apparatus  is  left  to 
cool  off  entirely,  in  order  to  prevent  the  black  from 
being  inflamed  by  contact  with  the  air.  The  cone  c 
is  then  lowered,  and  in  its  descent  scrapes  off  the  black 
sticking  against  the  sides.  The  black  is  removed 
through  an  iron  door  f,  which  is  kept  tightly  closed 
during  the  operation. 

The  black  obtained  by  this  process  is  used  for 
marine  and  oil  painting.  It  is  much  less  pure  when 
rosin  waste  is  employed,  since  it  contains  a  greater 
proportion  of  impurities  which  are  carried  over  with  it. 

Second  Process. —  Tar  Black, 

The  manufacture  of  lampblack  by  the  incomplete 
combustion  of  coal  tar,  is  cheaper  than  that  we  have 
just  described.  During  the  distillation  of  bituminous 
coal  for  making  gas,  there  are  produced  considerable 
quantities  of  tar,  which  has  several  applications  in 
the  arts,  one  of  which,  and  not  the  least  important,  is 
the  preparation  of  lampblack. 

The  apparatus  is  a  furnace  A  (Fig.  60),  lined  with 
firebricks,  and  which  contains  a  small  kettle  b.  A 
large  and  thick  cast-iron  pipe  c  is  fixed  to  the  upper 
part  of  A,  and  establishes  a  connection  with  a  large 
condensing  room,  built  of  stone  or  brick,  and  divided 


520 


MANUFACTURE  OF  COLORS. 


into  three  compartments  d,  e,  f,  of  unequal  sizes. 
The  black  settles  in  these  compartments,  which  com- 
municate with  each  other  by  means  of  holes  in  the 
partition  walls.  The  apparatus  ends  by  a  chimney  g, 
about  1  metre  high,  which  delivers  into  the  atmos- 
phere the  uncondensable  gaseous  products. 


Fig.  60. 


The  mode  of  operation  is  very  simple :  the  furnace 
is  first  brought  to  a  dark-red  heat,  and  then  the 
kettle  B  is  put  in.  The  tar  introduced  soon  becomes 
inflamed,  and  produces  an  abundance  of  smoke  which 
passes  through  the  pipe  c,  and  is  condensed  in  the 
compartments  d,  e,  f.  A  sliding  register,  in  front 
of  the  furnace,  allows  of  the  watching  of  the  opera- 
tion. When  the  combustion  of  the  tar  in  the  kettle 
B  is  complete,  a  new  quantity  of  material  is  added, 
and  so  on  for  several  consecutive  days.  In  order  to 
render  the  combustion  more  rapid,  the  tar  is  now  and 
then  stirred  with  an  iron  hook.  When  the  accumu- 
lation of  charred  residue  in  the  kettle  becomes  too 
considerable,  the  kettle  is  removed,  and  is  imme- 
diately replaced  by  a  clean  one  filled  with  coal  tar. 
One  of  the  most  essential  conditions  is  to  conduct  the 
combustion  with  a  minimum  of  air;  otherwise,  the 
yield  will  be  less,  and  the  product  will  have  a  russet, 


BI/ACK  COLORS. 


521 


and  sometimes  a  whitish  tinge,  which  will  depreciate 
its  market  value  considerably. 

The  solid  residue  left  in  the  kettles  may  be  em- 
ployed for  heating  the  furnace  at  the  beginning  of  an 
operation.  It  is  very  hard  and  compact,  and  requires 
to  be  removed  with  iron  tools. 

"We  have  ascertained  by  experiments  on  a  large 
scale,  that  1000  kilogrammes  of  good  coal  tar  wdll 
give  on  an  average  250  kilogrammes  of  lampblack, 
that  is,  a  yield  of  25  per  cent.  The  operation,  with 
this  quantity  of  material,  takes  six  days,  with  one 
furnace  and  one  man.  The  same  man  can  attend  to 
several  fires  at  the  same  time. 

When  one  furnace  is  used,  the  black  is  removed 
every  week  through  the  door  a,  which  is  hermetically 
closed  during  the  operation.  The  packing  of  the  250 
kilogrammes  of  black  requires  about  25  casks  of  400 
litres,  or  a  cask  for  about  10  kilogrammes  of  black. 

The  tar  should  be  free  from  earthy  substances,  or 
the  yield  will  be  less. 

The  same  apparatus  may  be  used  for  the  prepara- 
tion of  lampblack,  with  the  heavy  (dead)  oils  of  tar 
and  schist.  These  oils,  very  rich  in  carbon,  are  very 
advantageous  for  this  manufacture,  and  produce  a  very 
handsome  black  which  is  much  esteemed.  Lampblack 
is  sometimes  prepared  from  the  soft  pitch  left  after 
the  incomplete  distillation  of  coal-tar.  This  latter 
black  is  not  much  esteemed ;  but  its  quality  may  be 
improved  by  burning  the  pitch  with  the  dead  oils  of 
tar  and  schist. 

Third  Process. — Oil  or  lampblack. 

This  black  is  the  lightest  and  finest  of  all,  and  is 
obtained  by  burning  certain  kinds  of  oils,  the  vege- 


522  MANUFACTURE  OF  COLORS. 

table  ones  preferably,  in  lamps  of  a  peculiar  construc- 
tion.   The  apparatus  is  represented  in  Fig.  61. 


Fig.  61. 


A,  lamp,  the  liquid  level  of  which  remains  constant. 
It  is  fed  from  a  reservoir  b,  filled  with  oil.  At  the 
lower  part  of  A  there  is  a  bent  tube  c,  the  upper 
opening  of  which  is  on  the  same  level  as  the  oil  in  A. 
The  combustion  takes  place  with  the  aid  of  a  wick 
made  of  cotton  or  amianthus.  This  latter  substance 
is  preferable,  because  it  is  incombustible,  and  may  be 
used  quite  indefinitely.  The  flame  burns  under  a  cone 
D,  fixed  to  an  elbow-tube  opening  into  a  large  hori- 
zontal pipe  E.  This  pipe  cools  the  smoke,  and  con- 
denses the  water,  and  other  condensable  liquid  pro- 
ducts, formed  during  the  operation.  From  this  pipe, 
the  smoke  passes  through  a  series  of  large  sacks  f,  f, 
F,  six  metres  high,  and  one  metre  in  diameter,  which 
are  kept  open  at  the  top  and  bottom  by  funnels  of 
galvanized  h^on.  The  first  and  second  sacks,  and  the 
third  and  fourth,  are  connected  together  by  the  curved 
metallic  pipes  h,  h.  The  other  connections  at  the 
top  and  bottom  are  through  straight  pipes.  The 
lower  funnels  are  closed  by  plugs  i,  i,  i,  which  allow 


BLACK  COLORS. 


523 


of  the  extraction  of  the  black  after  each  operation. 
The  smoke  condenses  in  these  sacks,  and  the  product 
is  the  finer  as  the  oil  itself  is  purer.  The  black  con- 
densed in  the  last  sacks  is  also  purer  and  finer  than 
that  in  the  first  part  of  the  apparatus,  which  is  often 
somewhat  wet  and  oily.  Each  series  of  sacks  is  ter- 
minated by  a  conduit  J,  communicating  with  a  draft 
chimney  for  the  escape  of  the  uncondensable  products. 
A  damper  regulates  the  draft,  which  should  not  be 
too  strong  or  too  weak.  In  the  first  case,  the  black 
in  the  sacks  might  become  inflamed  ;  in  the  second, 
the  smoke  could  not  pass  through  the  whole  appa- 
ratus. 

The  operation  is  very  simple :  the  oil  is  kept  at  a 
constant  level  in  the  lamp,  by  keeping  the  reservoir 
B  filled;  and  the  damper  is  regulated  so  as  to  give 
sufl&cient  air  for  the  combustion. 

The  black  is  removed  when  a  certain  quantity  has 
accumulated  in  the  sacks.  Receivers,  barrels  for 
instance,  are  placed  under  each  funnel  i,  i,  i,  and, 
after  taking  oif  the  plugs,  the  sacks  are  gently  struck, 
so  as  to  detach  the  black.  In  this  manner,  the  various 
qualities  of  black  may  be  collected  separately,  and  we 
have  already  said  that  the  product  is  the  finer  and 
the  better  as  it  is  taken  from  the  sacks  further  from 
the  lamp. 

Experience  has  proven  that  the  same  process  may 
be  applied  to  the  combustion  of  the  dead  (heavy)  oils 
of  tar  and  schist.  These  oils  are  substituted  for  the 
vegetable  ones,  or  mixed  with  them,  in  the  lamps. 
The  operation  is  conducted  in  the  same  manner.  Of 
all  the  processes  of  manufacture  we  have  described, 
this  latter  gives  the  purest  black  with  the  least  waste, 
but  it  requires  fluid  materials. 


524 


MAI^^UFACTURE  OF  COLORS. 


Whatever  be  the  mode  of  preparation,  lampblack  is 
never  entirely  pure.  It  holds  fixed  and  volatile  salts, 
fatty  and  oily  substances,  various  pyrogeneous  pro- 
ducts, etc.  It  is  purified  by  a  calcination  in  thick 
sheet-iron  cylinders,  into  which  it  is  tightly  packed, 
and  which  are  heated  in  a  reverberatory  furnace. 
The  cylinders  may  generally  open  in  two  parts  by 
means  of  hinges,  and  it  is  then  easy  to  remove  the 
calcined  black.  But,  as,  after  this  operation,  the  pro- 
duct still  contains  various  salts,  it  may  be  treated  by 
dilute  hydrochloric  acid  for  ten  or  twelve  hours. 
Several  subsequent  washings  will  remove  the  acid 
and  the  soluble  salts.  The  black  which  has  been 
purified  in  this  manner  contains  but  a  trace  of  sili- 
cious  matter,  upon  which  the  acid  has  no  action. 

We  should  state  that  the  purification  of  lampblack 
is  tedious  and  expensive,  and  that  in  the  arts  it  is 
generally  used  as  it  comes  from  the  producing  appa- 
ratus. 

§  12.  Chrome  or  aniline  Hack, 

Mr.  W.  H.  Perkin  has  described  a  process  for 
obtaining  a  coloring  matter  from  a  solution  of  sul- 
phate of  aniline,  mixed  with  another  solution  of  a 
bichromate.  There  is  formed  a  black  precipitate, 
which,  being  purified  of  certain  brown  impurities,  may 
be  used  alone,  or  conjointly  with  lamp  or  ivory-black, 
for  the  preparation  of  printing  inks,  colors,  and  var- 
nishes. This  black  is  much  more  intense  than  lamp- 
black, which  always  has  a  brown  tinge. 

For  incorporating  this  aniline  or  chrome  black  with 
lampblack,  Mr.  J.  R.  Palmer  uses  25  parts  of  chrome 
black,  and  mixes  it  with  75  parts  of  lampblack  in  a 
mill.    The  product  is  passed  through  fine  copper 


BLACK  COLORS. 


525 


gauze  sieves,  and  is  received  in  a  leather  bag.  What 
remains  upon  the  sieve  is  ground  again.  The  chrome 
black  may  be  used  alone. 

§  13.  Various  hlacl^s. 

We  shall  conclude  our  remarks  upon  vegetable 
blacks  by  repeating  that,  for  certain  kinds  of  paint- 
ing, a  cliarcoal-hlack  is  employed,  which  results  from 
the  calcination  in  closed  vessels  of  any  kind  of  wood. 
This  charcoal  is  very  finely  comminuted,  and  is  washed 
in  order  to  remove  the  soluble  salts.  It  always  pos- 
sesses a  bluish  tinge. 

Mr.  W.  E.  Newton  has  recently  published  the 
details  of  a  peculiar  process  for  the  manufacture  of 
vegetable  blacks,  which  are  real  ulmin-blacks. 

"  All  the  blacks,"  says  he,  "  met  with  in  the  trade 
for  painting,  printing,  etc.,  are  slow  in  drying.  This 
inconvenience  is  remedied  by  mixing  with  the  carbon 
certain  earthy  or  alkaline  bases. 

"The  oxides  of  potassium,  sodium,  calcium,  and 
aluminium  may  be  employed  in  the  preparation  of 
the  new  blacks.  The  carbon  is  obtained  from  an 
organic  substance,  coal-tar,  for  instance,  on  account 
of  its  low  price.  The  oxides  are  introduced,  either 
in  the  caustic  state,  or  as  combinations,  which  may 
be  mutually  decomposed  at  the  time  of  mixing. 

"The  following  are  the  proportions  for  the  mix- 
tures :  100  kilogrammes  of  slaked  lime  are  mixed  with 
80  kilogrammes  of  coal-tar,  and  then  9  kilogrammes 
of  alum.  The  whole  is  made  into  a  homogeneous 
paste,  which  is  calcined  in  cast-iron  retorts,  like  bone- 
black.  When  the  carbonization  is  complete,  the  fire  is 
removed,  and  the  substances  are  left  to  cool  in  the 


526 


MANUFACTURE  OF  COLORS. 


closed  retorts.  Lastly,  the  black  is  removed,  and  is 
ready  to  be  ground. 

"By  varying  the  proportions  of  tar  and  slaked 
lime,  all  of  the  tones  and  hues  of  gray  and  brown  may 
be  obtained." 

The  following  is  another  mode  of  preparation  of 
vegetable  blacks,  which  is  described  in  vol.  87  of  the 
Brevets  Invention,  and  which,  notwithstanding  all 
it  claims,  will  probably  furnish  only  an  ulmin-brown. 

The  process  consists  in  carbonizing  any  kind  of 
vegetable  matter,  by  the  double  action :  first,  of  sul- 
phuric and  nitric  acids,  or  of  sulphuric  acid  alone; 
second,  of  heat.  The  action  may  be  modified  to  suit 
the  nature  of  the  substances  which  are  to  be  acted 
upon. 

For  instance,  and  in  preference  to  other  substances, 
we  take  the  saccharine  substance  resulting  from  the 
transformation  of  potato  starch  by  sulphuric  acid. 
This  syrup  is  dried,  and  mixed  in  an  iron  kettle  with 
12  to  15  per  cent,  of  nitric  acid,  or  14  to  18  per  cent, 
of  concentrated  sulphuric  acid. 

The  mixture  is  stirred  all  the  while,  and  is  heated 
at  from  100°  to  110°  C,  which  temperature  is  main- 
tained for  some  time.  Under  the  double  action  of  the 
heat  and  acids,  the  substance  becomes  gradually 
thicker,  and  is  converted  into  a  black  paste.  The 
paste  is  brown  when  the  operation  fails. 

"When,  from  comparative  color  tests  upon  a  plate, 
it  is  ascertained  that  the  greatest  intensity  of  black 
has  been  reached,  there  is  added  to  the  paste  from  2 
to  3  per  cent,  of  concentrated  sulphuric  acid.  The  fire 
is  urged  more  vigorously  under  the  kettle,  the  contents 
of  which  are  stirred  all  the  time,  in  order  to  prevent 
them  from  sticking  to  the  sides  of  the  kettle.  The 


BLACK  COLORS. 


527 


mass  soon  becomes  granular,  when  the  heating  is 
finished. 

After  cooling,  the  product  is  carefully  washed  in 
draining  troughs.  The  black,  thus  obtained  and  dried, 
is  of  a  perfect  color,  very  light,  and  easily  ground. 

The  process  is  also  successful  with  ordinary  flour, 
potato  starch,  or  any  amylaceous  substance,  with  any 
ligneous  or  fibrous  material,  with  rags,  paper,  wool, 
cotton,  the  leaves  of  trees,  the  pulp  of  beet  roots,  lin- 
seed cakes,  etc.,  in  fact  with  any  carbonaceous  sub- 
stance. Nevertheless,  we  should  prefer  flour,  potato 
starch,  and  the  syrup  of  glucose,  which  we  mentioned 
at  the  beginning. 

The  operator  will  easily  ascertain,  from  the  nature 
of  the  substance  to  be  worked,  how  he  should  modify 
the  proportions  of  nitric  and  sulphuric  acids,  and  the 
degree  of  heat.  An  increased  proportion  of  sulphuric 
acid  will  produce  a  more  rapid  and  energetic  carboni- 
zation, and  the  particles  of  black  will  be  lighter  and 
more  divided.  An  excess  of  heat  is  to  be  avoided, 
because  the  substance,  after  being  completely  dried  in 
the  kettle,  will  become  so  hard  that  it  will  be  difficult 
to  pulverize  it  afterwards. 

When  the  fluid  syrup  of  potato  starch  (glucose)  is 
employed,  the  acid  present  in  it  should  not  be  neutral- 
ized with  carbonate  of  lime  or  any  alkali.  The  syrup 
is  immediately  concentrated  by  evaporation,  and  less 
sulphuric  acid  is  to  be  mixed  with  it,  since  it  retains 
that  added  for  the  saccharification. 

The  best  substances  for  transformation  into  a  fine 
black,  are  those  which  make  transparent  solutions 
with  water.  These  substances  are  also  those  which 
are  the  more  easily  pulverized,  and  which  absorb  light 


528 


MANUFACTURE  OF  COLORS. 


more  readily.  Indeed,  absorption  of  light,  and  black 
coloration  are  the  same  phenomenon. 

This  new  black  replaces  lampblack,  and  those  from 
ivory,  bones,  and  charcoal.  Therefore,  it  may  be 
employed  for  the  manufacture  of  printing  ink,  of  that 
for  copperplate  printing,  of  blacking,  of  black  paints, 
and  of  any  other  material  requiring  a  durable  black 
for  a  basis. 

§  14.  Inks. 

Inks,  generally  speaking,  are  the  liquids  employed 
for  tracing  those  signs  which  represent  human 
thought ;  but  they  are  sometimes  employed  for  dyeing 
and  coloring  various  substances,  wood  for  instance. 

Inks  have  not  a  fixed  and  definite  composition. 
They  are  principally,  as  is  well  known,  a  combination 
of  a  solution  of  sulphate  of  iron  with  a  solution  of 
nut-galls,  in  which  the  precipitate  is  kept  in  suspen- 
sion by  means  of  a  gammy  substance,  which,  more- 
over, improves  the  fluidity  of  the  liquid. 

Besides  the  two  elements  of  the  black  compound, 
other  ingredients  are  added  in  order  to  produce  a 
more  intense  color,  or  a  more  pleasing  hue,  or  pecu- 
liar properties,  according  to  the  uses  for  which  it  is 
intended. 

Thus  it  is  that  we  find  formulae  for  inks  in  which 
there  are  decoctions  of  logwood  and  other  dye  woods, 
alum,  sugar,  molasses,  peroxide  of  manganese,  alka- 
lies or  alkaline  salts,  acids,  gelatin,  soap,  India  ink, 
lakes,  indigo,  lamp  and  other  blacks,  alcohol,  chloride 
of  mercury,  sulphate  of  copper,  catechu  and  other 
tannin  materials,  essential  oils,  resins,  isinglass,  mad- 
der, salts  of  chromium,  cobalt,  and  silver,  etc.  etc. 

There  are  many  other  fluids  of  the  same  kind,  some 


BLACK  COLOKS. 


529 


of  which  are  the  so-called  indelible  inks,  for  increas- 
ing the  security  of  commercial  transactions ;  others 
for  writing  with  metallic  pens ;  and  lastly,  those  for 
marking  linen,  or  for  tracing  colored  signs  or  draw- 
ings. 

Typography,  copperplate  printing,  lithography,  au- 
tography, etc.,  also  use  certain  compositions  called 
inks,  and  which  are  made  of  oil  varnish,  resins,  balms, 
blacks,  indigo,  metallic  salts,  tallow,  soap,  wax,  etc. 
etc. 

^e  cannot  here  examine  at  length  the  preparation 
of  these  various  products.  Their  composition,  which 
varies  ad  infinitum^  would  require  more  room  than 
can  be  had  in  this  volume.  "We  are,  therefore,  obliged 
to  refer  the  reader  to  our  Manuel  de  la  fabrication  des 
encres  of  the  Encyclopedie-Roret,  in  which  will  be 
found  all  the  formulae  which  have  been  found  advan- 
tageous in  practice. 

The  manufacturer  of  colors  may  undertake  the 
preparation  of  inks ;  but,  generally  in  large  cities,  it 
forms  a  speciality. 

C.  ANIMAL  BLACKS. 

§  15.  Bone  blacks. 

The  bones  of  animals  are  composed  of  water,  fat, 
albumen,  phosphates  of  lime  and  magnesia,  carbonate 
of  lime,  and  about  32  per  cent,  of  an  organic  sub- 
stance. When  the  bones  are  carbonized  at  a  red  heat 
in  a  closed  vessel,  the  organic  substance  is  decom- 
posed into  gases  and  volatile  liquids,  and  the  residue 
of  carbon,  mixed  with  the  earthy  salts,  forms  ani- 
mal or  bone  black.  Before  carbonizing  the  bones, 
they  are  boiled  in  order  to  remove  the  fat.  The  car- 
34 


530 


MAIirUFACTURE  OF  COLORS. 


bonization  is  done  in  closed  vessels,  and  retorts,  and 
the  cold  product  is  ground  and  passed  through  silk 
sieves. 

Bone  black  has  generally  a  reddish  reflex,  which  is 
believed  to  be  due  to  the  phosphate  contained  in  it, 
and  which  may  be  partly  removed  by  a  treatment 
with  hot  and  dilute  hydrochloric  acid.  After  rinsing 
with  water,  the  black  is  calcined  a  second  time. 

§  16.  Ivory  hlack. 

This  black  is  obtained  by  calcining  ivory  scraps  in 
a  clay  crucible  with  its  cover  luted  on,  in  such  a 
manner,  however,  that  the  gases  may  escape.  The 
crucible  is  brought  to  a  red  heat,  and  the  operation  is 
complete  when  gases  cease  to  burn  at  the  junction  of 
the  crucible  and  its  cover.  After  a  thorough  cooling, 
the  black  is  powdered. 

Thus  prepared,  this  black  is  of  the  first  quality  for 
painting.  It  is  brought  to  a  great  degree  of  commi- 
nution by  grinding  with  water,  either  with  a  slab  and 
muller,  or  between  two  horizontal  stones.  The  grind- 
ing should  be  continued  until  the  paste  is  perfectly 
smooth  and  homogeneous.  The  black  is  then  poured 
into  convenient  moulds,  and  dried  first  at  the  ordinary 
temperature,  and  afterwards  in  stove-rooms  heated  to 
from  80°  to  100°  C. 

We  should  state  that  most  of  the  black  sold  as 
ivory  black,  is  only  a  bone  black  of  the  first  quality. 

§  17.  Candle  hlach. 

Candle  black  is  very  light  and  of  a  splendid  and 
intense  color.  It  is  prepared  by  burning  candles 
made  of  animal  substances,  stearin  preferably,  under 
metallic  plates  or  funnels.     When  a  certain  proper- 


BLACK  COLORS. 


531 


tion  has  accumulated,  it  is  collected  delicately,  so  as 
not  to  compress  it,  and  so  as  to  preserve  its  lightness. 

§  18.  Prussian  hlacJc, 

This  is  the  product  of  the  calcination  of  Prussian 
blue  in  closed  vessels.  This  black  is  costly,  but  little 
employed,  and  advantageously  replaced  by  ivory  and 
lampblacks. 

§  19.  China  or  India  ink. 

This  is  a  composition,  the  basis  of  which  is  the 
finest  and  purest  lampblack.  The  calcined  oil  or 
lampblack  is  that  preferred  for  this  manufacture,  and 
gives  an  ink  of  the  first  quality,  which  is  much  em- 
ployed as  a  water  color.  It  is  used  in  England  for 
mezzo  tin  to  engravings,  and  the  hue  is  heightened  by 
a  small  proportion  of  carmine  lake.  This  ink  was 
discovered  in  China,  and  the  inhabitants  of  that 
country  had  for  a  long  time  the  monopoly  of  its  manu- 
facture. But  since  the  development  of  chemistry  and 
the  arts,  this  product  has  been  perfectly  imitated. 
Among  the  numerous  formulae  indicated  for  its  prep- 
aration, we  find  that  the  following  one  gives  a  pro- 
duct in  no  way  inferior  to  the  best  China  ink : — 


Calcined  lampblack  100  grammes. 

Shale  black  (Boghead)  in  impalpable  powder     50  " 
Indigo  carmine  in  cakes  .       .    ,   .       .  .10 

Carmine  lake  5  " 

Gum  Arabic  (first  quality)     .       .       .       .10  " 
Purified  ox-gall      .       .       .              .  .20 

Alcoholic  extract  of  musk      .       .       .       .       5  " 


The  gum  is  dissolved  in  50  to  60  grammes  of  pure 
water,  and  the  solution  filtered  through  a  cloth.  The 
indigo  carmine,  lake,  lampblack,  and  shale  black 


532 


MANUFACTURE  OF  COLORS. 


are  incorporated  with  this  liquor,  and  the  whole  is 
ground  upon  a  slab  with  a  muller,  in  the  same  man- 
ner as  ordinary  colors,  but  in  this  case  the  grinding 
takes  much  longer.  When  the  paste  is  thoroughly 
homogeneous,  the  ox-gall  is  gradually  added,  and 
then  the  alcoholic  extract  of  musk.  The  more  the 
black  is  ground,  the  finer  it  is.  For  the  above  quan- 
tities, the  grinding  should  last  at  least  twelve  hours. 

The  black  is  then  allowed  to  dry  in  the  air,  until  it 
has  acquired  sufficient  consistency  to  be  moulded 
into  cakes,  which,  in  their  turn,  are  still  further  dried 
in  the  air,  out  of  the  reach  of  dust.  When  quite  firm, 
these  cakes  are  compressed  in  bronze  moulds  having 
appropriate  designs  engraved  on  them.  The  moulded 
ink  is  then  wrapped  in  tinfoil,  with  a  second  envelope 
of  gilt  paper. 

The  ink  which  has  been  prepared  in  this  manner 
possesses  all  the  properties  of  the  real  Chinese  article. 
Its  grain  is  fine  and  smooth ;  it  flows  very  well,  mixes 
perfectly  with  many  other  colors,  and  becomes  so 
firmly  fixed  to  the  paper,  that  other  colors  may  be 
spread  over  it  without  washing  it  out. 

Gum  Arabic  might  be  replaced  by  gelatin ;  but  as 
this  latter  substance  is  easily  decomposed  and  putre- 
fied, we  prefer  gum  Arabic.  Moreover,  the  ink  is 
better,  and  flows  more  easily  upon  the  paper. 

SECTION  VI. 

GREEN  COLORS. 

§  1.  Green  Verona  earth. 

There  are  found  in  Italy,  near  Yerona,  in  France, 
Germany,  Hungary,  and  the  island  of  Cyprus,  certain 
earthy  masses  which  are  inclosed  in  the  amygdaloid, 


GREEN  COLORS.  533 

porphyric,  and  basaltic  rocks,  and  which  possess  a 
Celadon  green  color  when  seen  in  masses,  and  are  a 
light  green  when  powdered.  They  are  smooth  to  the 
touch  as  are  all  magnesian  earths,  and  smell  like 
clay.  Such  is  the  physical  appearance  of  Verona 
earth,  which  was  used  as  a  pigment  by  the  Greeks 
and  Romans,  and  which,  at  the  present  time,  is  washed 
and  employed  for  landscape  painting  on  account  of 
its  durability. 

Two  kinds  of  Verona  earth  are  found  in  the  trade : 
that  from  Verona,  and  that  from  the  island  of  Cyprus. 
The  Verona  article  is  of  a  purer  color,  and  has  been 
analyzed  by  Mr.  Berthier,  and  more  recently  by  Mr. 


Delesse.    Its  composition  is — 

Silica   51.21 

Alumina  1.25 

Protoxide  of  iron   20.72 

Magnesia  6.16 

Soda  '   .       .       .  6.21 

Water  4.49 


Protoxide  of  manganese  trace. 

The  earth  from  the  island  of  Cyprus  has  a  color 
intermediary  between  verdigris  and  apple-green.  Its 
analysis  by  Klaproth  gives — 


Silica   51.5 

Protoxide  of  iron   20.5 

Potassa   18.0 

Magnesia   1.5 

Water   8.0 


There  are  many  natural  green  substances,  which 
could  be  employed  in  the  arts,  and  which  possess 
tones  or  hues  different  from  that  of  Verona  earth. 
For  instance,  Poland  earth  is  a  leek-green ;  that  from 
Unghvar,  resulting  from  the  decomposition  of  tra- 


534 


MAJirUFACTUEE  OF  COLORS. 


chytes,  is  a  grass-green.  Small  granules  of  green 
earth  are  found  disseminated  in  the  coarse  limestones 
of  the  lower,  marine  deposits,  in  the  neighborhood  of 
Paris. 

§  2.  Malachite. 

This  green  substance  is  found  principally  in  Siberia, 
in  the  Oural  Mountains,  and  in  the  Bannate,  in  the 
Tyrol,  in  Saxony,  Bohemia,  England,  etc.  It  is  a 
native  hydrated  carbonate  of  copper  which  possesses 
different  hues.  It  is  also  caUed  mountain  green  and 
Hungary  green,  Reduced  to  a  very  fine  powder,  this 
substance  gives  a  magnificent  green,  which  is,  how- 
ever, too  expensive  to  be  largely  used.  It  has  been 
advantageously  replaced,  first,  by  the  greens  of 
Brunswick  and  of  Bremen,  and  afterwards,  by  that  of 
Schweinfurt  and  by  Mittis  green,  which  are  more  dura- 
ble than  the  two  former.  The  manufacture  of  these 
artificial  greens  will  be  described  further  on. 

§  3.  Iris-green, 

Iris-green  is  a  color  which  was  formerly  used  for 
miniature  painting ;  but  it  is  so  fugitive  that  it  has 
been  abandoned.  It  was  prepared  with  the  flower  of 
the  iris,  macerated  in  alum  or  gum-water.  The  so- 
lution was  filtered,  and  evaporated  in  dishes,  in  a  dark 
place. 

§  4.  Sap-green, 

Sap-green  is  a  dark  green  mass,  which  is  employed 
only  for  water  colors  and  the  manufacture  of  pastels. 
It  is  prepared  at  Nuremberg  and  in  the  south  of 
France.  We  reproduce  here  the  improvements  made 
by  Mr.  E.  de  Hagen,  and  which  are  described  in  the 
TecTinologiste^  vol.  xiv.  page  415. 


GREEN^  COLORS. 


535 


"Sap-green,  or  vegetable  green,  is  the  juice  of  the 
buckthorn  berry  {RJiammts  catharticus),  and  is  pre- 
pared by  various  processes,  which  do  not  always  pro- 
duce a  handsome  green,  but  often  result  in  a  greenish- 
yellow  color,  or  a  dirty  yellow,  or  a  grayish-yellow. 
The  green-yellow  coloration  is  generally  due  to  the 
employment  of  quite  ripe  berries,  and  the  grayish  or 
dirty  yellow  to  these  same  berries  after  they  have 
passed  their  maturity.  It  happens  sometimes  that 
sap-green,  when  put  upon  a  brush,  is  wanting  in 
transparency,  and  this  is  due  to  an  addition  of  car- 
bonate of  magnesia.  This  color  is  often  sticky  and 
viscous,  because  carbonate  of  potassa  has  been  mixed 
for  rendering  the  juice  green.  Lastly,  there  are  now 
to  be  found  in  the  trade  more  or  less  brown  sap-greens, 
because  they  have  been  evaporated  at  too  intense  a 
heat. 

"  All  of  these  properties  of  various  kinds  of  sap- 
green  are  often  united  in  a  greater  or  less  degree  in 
the  same  sample  of  green,  which  is  none  the  better 
for  it.  For  instance,  there  is  often  sold,  under  the 
name  of  sap-green,  a  yellowish  substance,  rendered 
opaque  by  the  presence  of  magnesia.  If  potassa  be 
added,  it  remains  shiny  and  yellow,  and  is  altered  when 
spread  with  the  brush.  Lastly,  certain  peculiarities 
of  sap-green  are  due  to  the  proj)ortions  of  its  con- 
stituent parts. 

"  As  I  have  had  the  opportunity  of  learning  several 
processes  for  the  manufacture  of  sap-green,  and  of  ex- 
perimenting upon  them,  I  think  that  it  may  be  useful 
to  give  some  particulars  as  to  the  manner  of  preparing 
a  very  fine  quality  of  this  color. 

"  In  order  to  prepare  a  fine  sap-green  of  a  decidedly 
green  color  and  translucent,  the  berries  employed 


536 


MANUFACTURE  OF  COLORS. 


should  not  have  reached  their  complete  maturity. 
Their  juice  will,  therefore,  not  appear  entkely  blue, 
but  somewhat  greenish.  The  boiling  of  the  berries 
and  the  evaporation  of  the  juice  should  be  done  at  a 
moderate  temperature.  A  charcoal  lire  may  be  em- 
plo3^ed  at  the  beginning,  but  the  evaporation  must  be 
finished  upon  a  water  bath.  Lastly,  the  green  color 
will  be  made  apparent  by  means  of  the  double  sul- 
phate of  alumina  and  potassa  (potassa  alum),  because 
this  salt  produces  the  finest  color,  gives  a  good  con- 
sistency to  the  mass,  and  preserves  the  transparency 
of  the  color  when  spread  with  a  brush.  Such  are  the 
main  conditions  in  the  preparation  of  a  good  sap- 
green  ;  and  as  it  is  important  to  know  the  proportions, 
we  give  as  a  formula  the  following  directions : — 

"  Any  given  quantity  of  buckthorn  berries,  not 
entirely  ripe,  are  boiled  with  a  small  proportion  of 
water  in  a  clean  copper  kettle,  and  upon  a  moderate 
charcoal  fire.  The  mass  is  continually  stirred,  until 
it  has  become  a  kind  of  magma,  which  is  pressed 
through  cloths.  The  residue  is  washed  and  pressed 
again.  The  liquors  are  left  to  settle,  and  are  filtered 
through  flannel  bags,  before  being  evaporated  to  the 
consistency  of  a  thick  extract,  upon  a  gentle  fire. 

"The  thickened  juice  is  then  weighed,  without 
pouring  it  out  from  the  kettle  (the  weight  of  which 
is  known),  and  to  every  kilogramme  of  liquor,  there 
are  added  65  grammes  of  alum  dissolved  in  water, 
and  the  mixture  is  thoroughly  stirred  all  the  while. 
The  evaporation  is  completed  upon  a  water  or  steam 
bath,  and  continued  as  long  as  practicable  without 
altering  the  color.  The  product  is  then  poured  into 
calf  bladders,  and  dried  in  the  air.  4ifv 

"  A  sap-green,  prepared  in  the  aforesaid  manner. 


GREEN^  COLOKS. 


537 


appears  black  when  viewed  in  masses,  and  a  fine 
green  by  looking  at  the  edges.  Spread  with  a  brush 
it  remains  transparent,  dries  rapidly,  and  produces  a 
handsome  leaf-green.  Exposed  to  the  air,  it  does  not 
become  damp.  To  sum  up,  it  presents  no  inconven- 
iences, and  is  all  that  can  be  desired. 

"  By  varying  the  proportions  of  alum,  different 
tones  of  green  will  be  obtained.  On  the  other  hand, 
should  it  be  desired  to  have  a  yellowish-green,  the 
riper  the  berries  the  more  yellow  the  color. 

"  Since  alum  gives  us  the  means  of  producing  the 
finest  qualities  of  sap-green,  we  should  reject  all  the 
other  substances  previously  employed,  such  as  mag- 
nesia, lime,  potassa,  etc.,  because  their  products  are 
always  defective  for  one  reason  or  another." 

§  5.  Picric  acid  green, 

Mr.  V.  Stein,  Professor  at  the  Paly  technical  School 
of  Dresden,  sends  us  a  few  particulars  regarding  this 
color. 

"  The  manufacture  of  artificial  flowers  has  already 
for  some  time  employed  a  green  of  various  tones  and 
hues,  which  equals  and  even  surpasses  the  finest 
Schweinfurt  green.  Analysis  shows  that  the  blue 
and  yellow  elements  of  this  green  are :  the  first,  the 
blue  of  the  sulpho-indigotate  of  potassa  (carmine  of 
indigo)  ;  and  the  second  or  yellow,  picric  acid,  also 
called  carbo-azotic,  binitro-phenic  acid. 

"Therefore,  by  mixing  solutions  of  picric  acid  and 
of  indigo  carmine,  there  is  obtained  a  very  fine  green, 
in  which  a  certain  proportion  of  gum  Arabic  may  be 
dissolved.  >It  is  probable  that,  when  this  green  is 
more  widely  known,  it  will  replace  the  Schweinfurt 


538 


MANUFACTURE  OF  COLORS. 


green  in  the  manufacture  of  paper  hangings,  at  least 
of  those  where  the  cost  is  a  secondary  consideration." 

§  6.  Bremen  green.    Bremen  hlue,    Verditer  Hue  and 

green, 

Mr.  J.  C.  Habich  has  published  in  the  Teclinologiste^ 
vol.  xvii.  p.  413,  very  complete  data  on  the  manufac- 
ture of  this  color,  which  was  previously  but  imper- 
fectly known.    We  here  reproduce  the  article. 

"  There  is  found  in  the  market,  under  the  names  of 
blue  and  green  verditer,  Bremen  blue,  Bremen  green, 
a  pigment  which  is  a  hydrated  oxide  of  copper, 
more  or  less  pure.  This  color,  prepared  for  the  first 
time  by  Kulenkamp  and  Hoffchlaeger,  of  Bremen, 
has  been  manufactured  by  several  methods,  which  are 
not  without  influence  upon  the  principal  properties 
of  the  product. 

"  The  hydrated  oxide  of  copper,  prepared  by  pre- 
cipitating a  neutral  and  soluble  salt  of  copper,  always 
forms,  in  drying,  a  dense  mass  with  a  conchoid  frac- 
ture. On  the  other  hand,  basic  and  insoluble  copper 
salts,  when  treated  by  alkalies,  furnish  porous  and 
pulverulent  colors.  In  accordance  with  the  acid  of 
the  copper  salt  and  the  process  followed,  the  color 
presents  more  or  less  variable  properties,  the  knowl- 
edge of  which  is  useful  to  the  consumer,  and  which 
should  certainly  be  attributed  to  the  different  modes 
of  preparation. 

"  In  the  beginning,  a  basic  chloride  or  oxychloride 
of  copper  was  always  employed,  and  although  the 
preparation  of  this  compound  with  metallic  copper 
(old  ship  sheathing)  was  done  by  different  processes, 
there  was  no  difference  in  the  properties  of  the  fin- 
ished color.    But  it  is  absolutely  necessary  that  the 


GREEN  COLORS. 


539 


pale  green  magma  should  contain  no  subchloride  of 
copper.  Let  us  now  examine  carefully  some  of  these 
modes  of  manufacture,  in  order  thoroughly  to  under- 
stand the  importance  of  the  condition  we  have  just 
stated. 

''There  are  mixed  in  large  wooden  tubs,  in  the 
construction  of  which  there  should  not  be  a  single 
iron  nail — 

"  1.  100  parts  of  old  copper  sheathing,  99  parts  of 
powdered  sulphate  of  potassa,  and  100  parts  of  chlo- 
ride of  sodium  (common  salt).  The  whole  is  moist- 
ened with  pure  water. 

"  2.  100  parts  of  copper,  60  of  common  salt,  and  30 
of  sulphuric  acid,  which  latter  has  been  diluted  with 
three  times  its  volume  of  water. 

"  3.  Or  there  is  poured  upon  the  copper  a  solution 
of  oxide  of  copper  (copper  scales)  in  pure  hydro- 
chloric acid. 

"  In  the  first  case  there  is  obtained  a  chloride  of 
copper,  which,  in  contact  with  more  metal,  becomes 
a  subchloride.  This  salt,  by  the  absorption  of  the 
oxygen  of  the  air,  is  transformed  into  the  basic  green 
compound  called  in  the  factories  oxide. 

"  In  the  second  case,  the  hydrochloric  acid  set  at 
liberty,  and  the  oxygen  of  the  air,  produce  the  same 
effects,  and  the  same  basic  salt  is  obtained. 

"  The  third  case  is  explained  in  the  same  manner. 

"Now,  as  the  subchloride  of  copper  (Cu^Cl),  de- 
composed by  caustic  alkalies,  precipitates  an  orange- 
yellow  suboxide  of  copper  (Cu^O),  it  is  evident  that 
there  should  remain  no  trace  of  this  subchloride. 

"  On  that  account,  in  several  factories,  it  is  cus- 
tomary to  prepare  the  magma  of  basic  oxychloride 
one  year  in  advance,  and  to  stir  it  frequently  before 


540 


MANUFACTUKE  OF  COLORS. 


it  is  used.  This  process  is  expensive,  since  the  in- 
terest of  the  capital  is  lost.  The  same  result  is  ob- 
tained by  entirely  drying,  now  and  then,  the  wet 
mixture.  In  this  manner  atmospheric  air  penetrates 
the  mass,  and  oxidizes  it  thoroughly. 

"  During  the  transformation  of  this  green  magma 
into  a  hydrated  oxide  of  copper,  an  interesting  phe- 
nomenon takes  place.  If  this  magma  be  introduced 
by  degrees  into  a  caustic  lye  of  potassa  or  soda, 
marking  about  20°  Be.,  the  product,  after  a  thorough 
washing  and  drying,  is  highly  comminuted,  covers  a 
great  deal,  and  becomes  darker  by  the  addition  of  a 
very  small  quantity  of  water.  If  the  magma  be  di- 
luted with  an  equal  volume  of  water,  the  mixture 
then  poured  at  once  into  an  excess  of  caustic  lye,  and 
the  whole  rapidly  stirred  and  then  let  to  rest,  a  few 
minutes  will  be  sufficient  for  the  materials  to  form  a 
mass,  which  can  scarcely  be  divided.  After  a  com- 
plete washing  and  drying,  the  color  is  much  lighter 
than  the  former  one,  but  it  covers  less.  Instead  of 
turning  darker  by  a  drop  of  water,  the  wet  spot  be- 
comes a  grayish-white,  which  disappears  on  drying. 

"  If  it  be  attempted  to  blue  the  precipitate  of  hy- 
drated oxide  of  copper,  obtained  by  any  of  the  above 
processes,  the  product  will  not  be  satisfactory,  since 
the  color  will  be  without  intensity  or  freshness.  On 
the  contrary,  a  good  result  will  be  obtained  by  adding 
to  the  magma,  before  its  treatment  with  the  alkaline 
lye,  a  small  proportion  of  a  concentrated  solution  of 
sulphate  of  copper.  It  appears  that  there  is  a  highly 
basic  sulphate  of  copper,  which  deepens  the  color; 
and  all  such  colors,  worked  in  this  manner,  contain 
a  small  amount  of  sulphuric  acid  and  of  alkali  (from 
the  lye  used). 


GREEiT  COLORS. 


541 


"  A  product,  covering  well,  can  be  prepared  as  fol- 
lows :  To  100  kilogrammes  of  the  thick  magma  of 
basic  oxychloride,  add  a  concentrated  solution  of  7 
kilogrammes  of  sulphate  of  copper,  and  then  40  kilo- 
grammes of  a  concentrated  caustic  lye  (32°  to  36° 
Be.),  Stir  the  mixture  vigorously  and  rapidly,  and 
pour  it  into  about  150  kilogrammes  of  caustic  lye, 
marking  20°  Be.  The  decomposition  is  thus  com- 
plete, and  the  precipitate  is  carefully  washed.  Before 
the  color  is  received  upon  the  filter  it  is  passed 
through  a  fine  hair  sieve.  Desiccation  at  a  high  tem- 
perature should  be  avoided,  so  as  not  to  change  the 
hydrated  state  of  the  copper  oxide.  It  is  no  less 
important  that  the  air  passing  through  the  stove- 
room  should  be  pure  and  free  from  acid  and  sulphur- 
etted fumes. 

"  The  process  which  we  have  just  described  is, 
with  slight  modifications,  nearly  everywhere  followed. 
But,  in  the  following  lines,  I  will  indicate  another 
method,  which  is  to  be  highly  recommended  to  color 
manufacturers. 

"  When  neutral  nitrate  of  copper  is  decomposed  by 
an  insufficient  proportion  of  a  solution  of  carbonate 
of  potassa,  the  flocculent  precipitate  of  carbonate  of 
copper  formed  at  first  is  gradually  transformed  into 
a  subnitrate  of  copper,  which  precipitates  in  the 
shape  of  a  heavy  green  powder.  If  this  basic  salt 
of  copper  be  treated  by  a  solution  of  oxide  of  zinc 
in  potassa,  there  is  formed  a  dark  blue  color,  which 
is  extremely  light,  and  with  great  covering  power. 
It  appears  to  be  a  zincate  of  copper,  with  a  very 
small  proportion  of  a  highly  basic  nitrate  of  copper. 

"  In  order  to  render  this  process  practical,  the  ope- 
ration will  be  conducted  as  follows  : — 


542 


MANUFACTURE  OF  COLORS. 


"  Copper  scales  are  calcined  in  a  reverberatory 
furnace  or  a  muffle,  until  all  the  suboxide  (Cu^O)  is 
transformed  into  protoxide  (CuO),  that  is  to  say, 
until  a  sample  dissolves  in  nitric  acid  without  the  pro- 
duction of  red  nitrous  vapors.  If  the  nitric  acid 
contains  hydrochloric  acid,  which  is  often  the  case, 
the  silver  which  may  be  present  in  the  copper  scales 
will  be  precipitated  in  the  form  of  chloride,  and  may 
then  be  collected. 

"The  solution  of  nitrate  of  copper  is  heated  and 
decomposed  by  a  clear  solution  of  carbonate  of  potassa. 
As  soon  as  the  effervescence  diminishes  in  intensity, 
the  solution  of  carbonate  of  potassa  is  added  by  small 
quantities  at  a  time,  until  there  remains  but  little 
undecomposed  copper  in  the  solution.  In  order  to 
collect  this  remainder  of  metal,  the  clear  liquor  is 
decanted,  and  the  green  precipitate  is  washed  several 
times  with  small  quantities  of  water.  All  the  liquors 
are  collected,  and  the  remaining  copper  is  precipitated 
by  a  solution  of  potassa.  The  green  carbonate  of 
copper  is  introduced  into  a  new  solution  of  nitrate  of 
copper,  in  which  it  is  transformed  into  a  basic  salt. 
The  previous  liquors  are  evaporated,  and  leave  crys- 
tals of  nitrate  of  potassa. 

"  An  economical  solution  of  oxide  of  zinc  is  made 
as  follows  :  Clippings  of  metallic  zinc  are  treated 
in  a  cast-iron  vessel  with  a  caustic  solution  of  potassa 
or  soda.  Hydrogen  is  immediately  disengaged,  and 
the  alkali  becomes  saturated  with  the  oxide  of  zinc, 
which  plays  the  role  of  an  acid.  When  the  liquor  is 
clear,  it  is  employed  for  the  decomposition  of  the 
basic  nitrate  of  copper.  The  product  is  a  handsome 
and  light  Bremen  blue,  and  the  evaporated  liquor, 


GREEN"  COLORS. 


543 


when  potassa  has  been  used,  gives  crystals  of  nitrate 
of  potassa. 

"  The  advantage  of  this  process  is  based  principally 
upon  the  preparation  of  a  cheap  nitrate  of  copper 
(since  nitric  acid  may  at  a  moderate  cost  be  extracted 
from  nitrate  of  soda),  and  upon  the  production  of 
nitrate  of  potassa,  which  is  a  valuable  secondary 
product." 

§  7.  Brunswick  green. 

Hydrochloric  acid  can  be  had  at  a  very  low  price 
in  certain'  localities,  and  is  used  for  extracting  the 
copper  from  poor  oxidized  ores.  !N^evertheless,  this 
acid  has  scarcely  any  effect  upon  those  ores  which 
are  not  oxidized,  and  it  is  necessary  to  add  now  and 
then  a  small  proportion  of  nitric  acid.  A  cheaper 
process  consists  in  moistening  the  ore  with  hydro- 
chloric acid,  and  exposing  it  to  the  contact  of  the 
atmosphere.  The  metal  then  becomes  easily  attacked 
by  chlorine,  and  even  by  solutions  of  chloride  of  am- 
monium and  of  common  salt.  The  subchloride  pro- 
duced is  rapidly  transformed  into  oxy chloride,  and 
forms  a  fine  light  green  called  Brunswick  green. 

§  8.  Scheele^s  green. 

Oxide  of  copper,  combined  with  various  substances, 
produces  quite  a  number  of  green  colors,  which,  un- 
happily, are  highly  poisonous,  but  possess  great 
brightness.  The  oldest  of  these  colors  is  a  neutral 
arsenite  of  copper,  discovered  in  1778  by  Scheele. 
The  formula  as  given  by  the  illustrious  Swedish 
chemist  is  as  follows  : — 

Dissolve,  in  a  copper  kettle,  1  kilogramme  of  pure 
sulphate  of  copper  in  20  litres  of  water.    In  another 


544 


MANUFACTURE  OF  COLORS. 


vessel  prepare  an  arsenite  of  potassa  by  boiling  1 
kilogramme  of  carbonate  of  potassa  and  325  grammes 
of  arsenious  acid  in  6  litres  of  water.  These  two 
solutions  are  filtered,  and  while  they  are  still  hot,  the 
arsenite  of  potassa  is  slowly  poured  into  the  solution 
of  sulphate  of  copper,  which  is  stirred  all  the  while. 
The  precipitate  of  arsenite  of  copper  settles  in  the 
liquor,  which  has  become  a  solution  of  sulphate  of 
potassa.  This  is  decanted,  and  the  precipitate  is 
carefully  washed  with  hot  water,  drained  upon  a 
cloth,  and  dried  at  a  low  temperature.  The  product 
is  about  1200  grammes  of  a  fine  green  color. 

This  product,  we  have  already  said,  is  a  neutral 
arsenite  of  copper  ;  but  it  may  be  rendered  basic  by 
increasing  the  proportion  of  sulphate  of  copper.  The 
color  is  finer,  but  not  so  durable. 

In  the  process  actually  followed  by  manufacturers, 
a  solution  holding  at  the  same  time  arsenious  acid 
and  the  sulphate  of  copper,  is  precipitated  by  one  of 
carbonate  of  potassa,  which  is  added  by  small  quan- 
tities at  a  time,  until  the  color  has  acquired  its  greatest 
brightness.  The  liquors  are  stirred  during  the  whole 
precipitation. 

Scheele's  green  may  be  used  with  water  or  oil,  and 
was  formerly  much  employed  especially  in  the  manu- 
facture of  paper-hangings.  It  is  now  replaced  by 
Schweinfurt  green,  which  has  more  durability. 

Another  sort  of  Scheele's  green,  called  green  lalce, 
is  prepared  in  this  manner:  A  solution  is  made  of  1 
kilogramme  of  tartrate  of  potassa  and  600  grammes 
of  arsenious  acid  in  8  litres  of  water,  which,  after 
filtration,  receives  a  solution  of  sulphate  of  copper 
poured  slowly  in.  The  mixture  is  kept  stirred  all  the 
while.    After  settling  and  decantation,  the  precipi- 


GREEN  COLORS. 


545 


tate  is  washed  with  clear  and  cold  water,  and  dried 
in  the  stove-room. 

§  9.  Schweinfurt  green. 

Schweinfurt  green  is  a  combination  of  acetate  and 
arsenite  of  copper,  the  color  of  which  varies  from  a 
dark  to  a  pale  green,  and  which  is  employed  in  all 
kinds  of  painting  and  in  the  manufacture  of  paper- 
hangings.  There  are  several  processes  of  manufac- 
ture which  we  shall  indicate. 

First  Process. 

This  process  is  due  to  Baron  Liebig,  and  is  as  fol- 
lows :  One  part  of  verdigris  is  heated  in  a  copper  kettle 
with  sufficient  distilled  vinegar  to  be  dissolved,  then 
one  part  of  arsenious  acid,  dissolved  in  water,  is  added. 
The  mixture  of  these  substances  produces  a  dirty 
green  precipitate,  which  is  dissolved  in  a  new  quan- 
tity of  vinegar.  After  boiling  for  some  time,  a  new 
precipitate  appears,  which  is  granular,  crystalline, 
and  of  a  magnificent  green.  It  is  separated  from  the 
liquor,  carefully  washed,  and  drained. 

If  the  liquor  still  contains  copper,  arsenious  acid 
is  added ;  and  conversely,  if  arsenious  acid  be  in  ex- 
cess, acetate  of  copper  is  introduced.  Lastly,  should 
it  contain  an  excess  of  acetic  acid,  it  is  used  again 
for  dissolving  verdigris. 

In  order  to  deepen  and  brighten  the  color  of  the 
product,  which  is  slightly  bluish,  it  is  boiled  with  one- 
tenth  of  its  weight  of  commercial  potash. 

Second  Process. 

This  Schweinfurt  green  is  prepared  by  mixing  10 
parts  of  acetate  of  copper  with  a  suflicient  quantity 
35 


546 


MANUFACTURE  OF  COLORS. 


of  water,  heated  at  50°  C,  to  make  a  liquid  and 
homogeneous  magma,  to  which  is  added  a  solution 
of  8  parts  of  arsenious  acid  in  100  parts  of  boiling 
water.  The  whole  is  kept  boiling.  It  is  sometimes 
necessary  to  add  a  small  quantity  of  acetic  acid  to 
the  mixture,  in  order  to  obtain  a  finer  color  with  a 
crystalline  appearance.  The  precipitate  is  collected 
upon  a  filter,  drained,  and  dried. 

The  decanted  liquor  is  advantageously  used  for 
dissolving  the  arsenic  of  a  new  operation.  The  solu- 
tion will  be  facilitated  by  the  addition  of  carbonate  of 
potassa,  which  forms  an  arsenite  of  potassa. 

Third  Process. 

This  process  has  been  described  by  Mr.  Braconno 
who  prepares  the  green  as  follows : — 

Dissolve  6  parts  of  sulphate  of  copper  in  a  small 
qviantity  of  hot  water,  and  prepare  another  solution 
by  boiling  in  water  6  parts  of  arsenious  acid  with  8 
parts  of  commercial  carbonate  of  potassa.  When 
carbonic  acid  is  no  longer  disengaged,  the  two  liquors 
are  mixed  while  being  stirred.  There  is  formed  an 
abundant  precipitate  of  a  dirty  greenish-yellow  color, 
which,  by  the  addition  of  a  slight  excess  of  acetic 
acid,  becomes  crystalline  and  of  a  fine  green.  It  is 
washed  with  boiling  water,  collected,  and  dried. 

Fourth  Process. 

This  process  is  due  to  Mr.  WingenSj  a  manufac- 
turer of  colors.  From  9  to  10  kilogrammes  of  arse- 
nious acid  are  dissolved  in  hot  and  pure  water,  and 
500  grammes  of  potassa  are  added  to  it.  After 
stirring,  and  settling  for  a  few  hours,  the  precipitate 
is  collected  upon  a  cloth.    (The  author  has  omitted 


GREEN  COLORS. 


547 


to  indicate  the  proportion  and  the  kind  of  copper  salt 
necessary  to  produce  the  above  precipitate. — Trans.) 

There  are  probably  other  processes  for  obtaining 
different  tones  and  hues  of  this  green,  which  are 
caused  by  varying  the  proportions  of  the  materials, 
or  by  other  substances  added  fraudulently  or  other- 
wise. A  pure  Schweinfurt  green  is  entirely  soluble 
in  nitric  or  hydrochloric  acid. 

The  commercial  sulphate  of  copper  generally  used 
for  the  manufacture  of  arsenical  greens  is  often  con- 
taminated with  sulphate  of  iron,  which  considerably 
impairs  the  purity  and  the  brightness  of  these  colors. 
Mr.  A.  Bacco  has  indicated  a  simple  and  economical 
process  for  removing  the  iron  from  solutions  of  sul- 
phate of  copper.  A  gelatinous  precipitate  of  car- 
bonate of  copper  is  produced  by  decomposing  a  solu- 
tion of  sulphate  of  copper  with  one  of  carbonate  of 
soda.  The  precipitate  is  washed,  and  a  suitable 
quantity  of  it  is  added  to  the  solution  of  sulphate  of 
copper  to  be  purified.  After  stirring,  the  mixture 
soon  deposits  flakes  of  oxide  of  iron,  and  the  clear 
liquor  contains  only  a  pure  sulphate  of  copper. 

§  10.  Mittis  green.    Vienna  green.   Kircliberger  green, 

Mittis  green  is  an  arseniate  of  copper,  which  is 
prepared  by  dissolving  20  parts  of  arseniate  of  potassa 
in  100  parts  of  hot  water,  and  mixing  this  solution 
with  another  of  20  parts  of  sulphate  of  copper. 
During  the  whole  operation  the  mixture  is  stirred. 
There  is  formed  a  pulverulent  precipitate  of  a  light- 
green  or  grass-green  color,  which  is  washed  and  dried. 
By  varying  the  proportions,  several  tones  and  hues 
are  produced.  But  in  the  commercial  article  these 
variations  are  generally  due  to  the  introduction  of 
foreign  substances. 


548 


MANUFACTURE  OP  COLORS. 


The  arseniate  of  potassa  is  prepared  by  boiling 
arsenious  acid  in  concentrated  nitric  acid,  filtering, 
and  saturating  with  carbonate  of  potassa,  and  crystal- 
lizing the  arseniate. 

§  11.  Oreen  ashes. 

These  green  ashes  are  prepared  as  follows :  1  part 
of  caustic  lime  and  2  parts  of  arsenious  acid,  with  a 
sufficiency  of  water,  are  boiled  together.  This  solu- 
tion of  arsenite  of  lime  is  decanted  or  filtered  clear, 
and,  while  it  is  still  hot,  it  is  stirred  at  the  same  time 
that  it  receives  a  solution  of  sulphate  of  copper.  The 
precipitate  is  a  green  powder  of  sulphate  of  lime 
and  of  arsenite  of  copper,  which  is  washed  and 
dried. 

Green  ashes  are  used  only  for  coloring  prints,  since 
they  do  not  possess  sufficient  body  for  oil  colors. 

§  12.  German  green  without  arsenic. 

For  some  time  past  there  has  been  sold  in  Germany 
a  green  without  arsenic^  which  is  intended  as  a  substi- 
tute for  the  arsenical  Schweinfurt  green.  This  color 
is  not  so  bright  as  the  latter,  is  in  the  shape  of  light 
and  crumbling  cubes,  and  may  be  applied  to  many 
purposes,  although  it  is  poisonous. 

"We  are  not  acquainted  with  the  preparation  of  this 
color.    An  analysis  made  by  Mr.  C.  Struve  shows  its 


composition  to  be — 

Chromate  of  lead   13.65 

Basic  carbonate  of  copper    ....  80.24 

Oxide  of  iron  0.77 

Carbonate  of  lime  2.65 

Water  2.58 


99.89 


GREEN  COLORS.  549 


This  green  is  very  durable,  and  has  more  body  than 
Schweinfurt  green. 

§  13.  JErlaa  green. 

According  to  Mr.  "Weilhem,  Erlaa  green  is  pre- 
pared in  the  following  manner,  in  a  small  town  of 
Saxony  which  bears  that  name. 

Pure  sulphate  of  copper  and  30  per  cent,  of  its 
weight  of  common  salt,  are  dissolved  in  water.  100 
parts  of  this  solution  are  poured  into  a  milk  of  lime, 
composed  of  300  parts  of  water,  and  from  40  to  50 
parts  of  white  and  well-burned  lime.  As  soon  as 
the  blue  color  appears  there  are  added  from  8  to  12 
parts  of  a  soluble  chrome  salt,  the  neutral  chromate 
of  potassa  being  preferred.  The  color  is  washed 
with  water,  and  immediately  pressed. 

Other  copper  salts,  or  a  greater  or  less  proportion 
of  lime  or  of  chromic  salt,  will  result  in  a  great  va- 
riety of  hues  of  this  color. 

§  14.  Mineral  green. 

This  color  is  but  little  used  in  the  arts,  because  it 
does  not  cover  enough.  It  is  a  mixture  of  hydrated 
oxide  of  copper  with  a  greater  or  less  proportion  of 
arsenite  of  copper.  It  is  prepared  by  precipitating, 
with  caustic  potassa,  a  solution  of  sulphate  of  copper 
and  12  to  15  per  cent,  (of  the  weight  of  the  sulphate) 
of  arsenious  acid  (white  arsenic).  If,  as  Mr.  Habich 
advises,  there  be  added  to  the  precipitate  a  solution 
of  zincate  of  potassa,  prepared  in  the  manner  pre- 
viously explained  (see  Bremen  green  or  Yerditer), 
there  is  obtained  a  very  bright  and  not  too  expensive 
color  of  a  light  green.    100  kilogrammes  of  copper 


550  MANUFACTURE  OF  COLORS. 


(sulphate  of?)  and  15  kilogrammes  of  arsenious  acid 
and  alkaline  zincate,  furnish  93  kilogrammes  of  color. 

Another  mineral  green  of  an  apple-green  color,  with 
a  bluish  reflex,  covering  and  drying  well,  but  turning 
black  easily,  is  prepared  from  a  mixture  of  2  parts  of 
Scheele^s  green,  6  parts  of  white  lead,  2  of  black  oxide 
of  copper,  3  of  mountain  blue,  and  one-half  part  of 
neutral  acetate  of  lead. 

§  15.  Paul  Veronese  green. 

We  are  not  acquainted  with  the  mode  of  prepara- 
tion of  this  fine  and  durable  color.  It  is  another 
arsenite  or  arseniate  of  copper,  made  in  Alsace  and  in 
England,  high  in  price,  and  used  either  for  water  or 
oil  painting. 

§  16.  English  green, 

English  green,  of  which  there  are  innumerable 
varieties  in  the  trade,  is  a  Scheele's  green  mixed, 
while  in  paste,  with  sulphate  of  baryta  or  sulphate  of 
lime,  tempered  with  a  small  quantity  of  water.  Its 
hue  varies  from  an  apple-green  to  that  of  a  dead  leaf. 
It  is  employed  with  water  and  oil,  but  generally  alone, 
because  it  alters  other  colors, 

§  17.  Neuwied  green. 

A.  16  parts  of  sulphate  of  copper,  dissolved  in  hot 
water,  are  decomposed  by  a  solution  of  arsenious 
acid.  On  the  other  hand,  4  parts  of  well-burned  lime 
are  slaked,  and  mixed  with  cold  water,  so  as  to  make 
a  milk  of  lime,  which  is  poured  through  a  fine  hair 
sieve  into  the  arsenical  solution  of  copper,  the 
latter  being  kept  constantly  stirred.  The  resulting 
green  color  is  washed  several  times.    Other  quali- 


GREEN  COLORS. 


551 


ties  of  this  pigment  are  prepared  by  the  following 
recipes : — 


The  color  cMed  picJcel  griin  in  Germany  is  prepared 
in  the  same  manner,  with  a  proportion  of  arsenious 
acid  equal  to  3.750  to  4.000  kilogrammes. 

§  18.  Milory  green.    Silk  green.    Green  cinnabar. 
Leaf  green. 

The  real  mode  of  manufacture  of  this  fine  color  is 
still  unknown.  It  is  found  in  the  market  in  the  shape 
of  troches,  it  unites  with  other  colors  well,  and  is  em-  ' 
ployed  for  oil  painting.  It  is  imitated  to  a  certain  ex- 
tent, by  mixing  together,  and  in  certain  proportions, 
ferrocyanide  of  potassium,  sulphate  of  iron,  acetate 
of  lead,  and  chromate  of  potassa.  A  few  chemists 
certify  that  there  is  also  some  sulphate  of  baryta. 

These  greens,  according  to  Mr.  Arnaudon  (  Techno- 
logiste,  vol.  xx.  p.  519),  are  intimate  mixtures  of 
chrome  yellow  and  Prussian  bkie,  with  an  addition  of 
alumina,  or  of  other  neutral  and  colorless  bases  or  salts. 
These  greens  possess  a  certain  brightness  and  great 
body,  but  they  participate  in  the  inconveniences  of 
binary  colors  (mixtures  of  two  simple — primary — 
colors,  yellow  and  blue,  in  this  case),  that  is,  their 
color  changes  and  their  brightness  diminishes  under 
artificial  light.  These  greens,  moreover,  do  not  resist 
alkalies,  which  destroy  the  blue  and  produce  a  brown- 
yellow.    Acids,  by  the  destruction  of  the  chrome 


B.  Sulphate  of  zinc  (copper?) 
Arsenious  acid  . 
Lime  .... 


8.000  kilogrammes. 


1.250 
1.000 
8.000 
0.750 
2.000 


C.  Sulphate  of  copper 
Arsenious  acid  . 
Lime  .... 


552 


MANUFACTURE  OF  COLORS. 


yellow,  render  the  blue  predominating.  They  are 
altered  by  solar  light,  and  darken  by  the  action  of 
the  sulphur  held  in  other  pigments,  such  as  vermilion, 
orpiment,  etc.,  with  which  they  may  be  mixed. 

Prussian  green  is  a  color  which  is  prepared  by 
pouring  a  solution  of  ferrocyanide  of  potassium,  into 
one  of  a  soluble  cobalt  salt  (nitrate,  sulphate,  chlo- 
ride). Its  hue  is  very  rich,  but  readily  turns  to  a 
reddish-gray. 

Binary  mineral  greens,  more  durable  than  the  pre- 
ceding, may  be  prepared  from  mixtures  of  the  yellows 
of  sulphide  of  cadmium,  Naples  yellow,  and  the  chro- 
mates  of  baryta,  tin,  and  zinc,  with  the  blues  of  ultra- 
marine and  of  cobalt.  They  are  not  blackened  by 
sulphuretted  gases. 

§  19.  Green  of  stannate  of  copper. 

The  color  of  this  green,  in  the  opinion  of  Mr.  Gen- 
tele,  is  not  inferior  to  that  of  arsenic  greens.  Among 
the  many  formulae  given  for  its  preparation,  the  fol- 
lowing is  one  which  gives  a  good  product : — 

To  a  solution  of  125  parts  of  sulphate  of  copper  in 
pure  rain-water,  there  is  added  a  solution  of  59  parts 
of  tin  in  nitric  acid.  This  mixture  is  precipitated  by 
an  excess  of  caustic  soda.  The  green  color  is  washed 
and  dried. 

A  less  handsome  green  is  prepared  as  follows : — 
100  parts  of  nitrate  of  soda,  and  59  parts  of  tin,  are 
brought  to  a  red  heat  in  a  Hessian  crucible.  When 
the  mass  is  cold,  it  is  dissolved  in  a  dilute  caustic  lye. 
This  solution  is  allowed  to  become  clear,  when  it  is 
diluted  with  more  water,  and  poured  into  a  solution 
of  sulphate  of  copper.    The  reddish-yellow  precipi- 


GREEN  COLORS. 


553 


tate,  soon  becomes  of  a  handsome  green,  by  washing 
and  drying. 

§  20.  Eisner  green. 

This  copper-green,  in  which  there  is  no  arsenic,  is 
not  so  bright  as  those  of  arsenic.  ^Nevertheless,  the 
various  hues  found  in  Germany  are  good  pigments, 
which  are  not  entirely  devoid  of  brightness,  and  are 
less  dull  than  green  ultramarine. 

These  green  colors  are  prepared  by  pouring  a  de- 
coction of  yellow  wood,  clarified  by  gelatin,  into  a 
solution  of  sulphate  of  copper,  and  adding  to  the 
mixture  from  10  to  12  per  cent,  of  tin-salt  (protochlo- 
ride  of  tin).  The  whole  is  precipitated  by  an  excess 
of  caustic  potassa  or  soda.  The  deposit  is  thoroughly 
washed,  and  its  green  color  acquires  a  bluish  tinge 
by  drying.  A  more  yellowish  hue  is  obtained  by 
increasing  the  proportion  of  yellow  wood. 

§  21.  Green  cinnabar. 

We  have  already  indicated,  in  the  article  on  chrome 
yellows,  the  preparation  of  a  green  color,  which  is  a 
mixture  of  chrome  yellow  with  Paris  blue.  There 
is  sold  in  Germany,  under  the  name  of  green  cinnabar 
(Grilner  zinnoher),  a  color  of  the  same  kind  and 
without  arsenic,  the  hue  or  tone  of  which  varies  from 
a  dark  to  a  light  green.  Mr.  L.  Eisner  recommends 
the  following  mode  of  manufacture  : — 

A  solution  of  yellow  chromate  of  potassa  is  mixed 
with  another  of  ferrocyanide  of  potassium  (yellow 
prussiate  of  potassa).  Another  separate  mixture  is 
made  of  neutral  acetate  of  lead,  and  of  proto-acetate 
of  iron,  which  is  prepared  by  decomposing  a  solution 
of  subacetate  of  lead  with  one  of  sulphate  of  iron. 


554 


MAI^UFACTURE  OF  COLORS. 


By  the  reaction,  an  insoluble  sulphate  of  lead  is 
formed,  and  the  proto-acetate  of  iron  remains  in  the 
solution.  It  is  the  clear  liquor  which  is  used;  but 
this  acetate  of  iron  may  be  prepared  by  other  pro- 
cesses. 

The  first  mixture  is  poured  into  the  second,  and 
there  is  formed  a  more  or  less  dark  precipitate,  which 
is  washed  and  dried  at  a  low  temperature.  Dark 
tones  are  obtained  by  having  the  iron  and  the  ferro- 
cyanide  predominating;  and  the  light  ones  by  an 
excess  of  lead  and  of  chromate. 

§22.  Gi 

China  green, 

A  green  lake  is  generally  a  color  prepared  with 
the  lake  of  a  yellow  coloring  substance,  mixed  with 
Prussian  blue.  These  pigments  give  very  handsome 
colors,  which,  however,  in  a  majority  of  cases,  possess 
but  slight  durability. 

The  green  lakes  and  the  vegetable  greens,  accord- 
ing to  Mr.  Arnaudon,  may  be  divided  into  three  cate- 
gories. 

The  first  of  these  categories  comprises  the  com- 
pound greens,  formed  by  the  mixture  of  a  vegetable 
blue  and  a  mineral  yellow,  and  conversely.  For  in- 
stance, indigo-carmine  with  the  yellows  of  chrome, 
Naples,  Cassel,  Yerona  (oxychloride  of  lead),  orpi- 
ment,  and  cadmium.  These  greens,  especially  those 
in  which  the  ^^ellow  is  a  chromate  or  a  sulphide,  are 
easily  altered  by  some  oxidizing  or  reducing  action. 
In  the  converse  case,  that  is,  when  the  blue  is  of 
mineral,  and  the  yellow  of  vegetable  origin,  for  in- 
stance, Prussian  blue,  molybdenum  blue,  ultramarine 
blue,  etc.,  associated  with  gamboge,  stil-de-grain, 


GREEN  COLORS. 


555 


woad,  etc.,  we  have  still  to  fear  the  mutual  alterations 
of  the  two  component  colors.  Thus,  Prussian  blue, 
in  contact  with  an  organic  substance,  turns  b}^  degrees 
to  a  black,  while  the  mixed  yellow  becomes  brown. 
Ultramarine  itself  becomes  paler,  if  the  yellow  de- 
velops any  acidity.  In  regard  to  the  green  with 
molybdenum  blue,  the  destruction  of  the  color  is 
ordinarily  due  to  an  oxidation  of  the  molybdenum 
compound. 

The  second  category  is  composed  of  the  compound 
greens  resulting  from  a  mixture  of  vegetable  yellows 
and  blues ;  for  instance,  indigo  blue  with  woad  yel- 
low, Indian  yellow,  and  the  yellows  of  gardenia  and 
hroussonetia.  Although  these  greens  cannot  be  con- 
sidered fast  colors,  they  are  nevertheless  superior  to 
the  preceding  ones  from  the  harmony  in  their  lighter 
tones  and  hues.  The  more  solid  greens  of  this  cate- 
gory are  those  formed  of  indigo,  associated  with  the 
yellows  of  Persian  berries,  woad,  and  gardenia,  and 
Indian  yellow. 

In  water  color  painting,  it  is  possible  to  employ  a 
mixture  of  picric  acid,  or  of  picrate  of  ammonia 
with  indigo  carmine.  But  this  green  is  not  durable, 
and  painting  exposed  to  solar  light  for  several 
months  becomes  yellowish,  then  yellow,  and  lastly, 
russet,  from  a  mutual  decomposition  of  the  picric 
acid  and  indigo. 

In  the  third  category  of  vegetable  lakes  we  have 
the  green  lake,  made  of  a  naturally  green  coloring 
substance,  united  to  a  colorless  metallic  oxide. 
For  instance,  grass-green  is  chlorophyl  associated 
with  lime  ;  sap-green  is  the  coloring  substance  ex- 
tracted from  the  bark  or  berries  of  the  buckthorn, 
and  precipitated  by  lime  or  alumina.    China  green 


556 


MANUFACTURE  OF  COLORS. 


is  to  be  added  to  the  list,  although  it  is  still  too  ex- 
pensive to  be  used  for  ordinary  paints. 

This  last  green,  in  daylight,  presents  nothing 
extraordinary,  and  its  bluish-green  hue  makes  it  re- 
semble green  ultramarine.  But,  under  artificial  light, 
it  acquires  a  bi-ightness  and  a  purity  of  color,  which, 
united  to  its  perfect  solubility,  renders  it  a  precious 
dye  for  those  tissues  which  are  intended  to  shine 
under  artificial  light.  This  green  stands  quite  well 
the  action  of  the  air,  but  to  a  much  less  extent  than 
indigo,  and  does  not  well  resist  the  influence  of  alka- 
line fumes.  Acids  change  China  green  to  a  violet- 
blue. 

§  23.  Mineral  green  lake. 

This  lake  is  a  mixture  of  the  oxides  of  copper  and 
zinc,  which  is  prepared  by  precipitating  with  carbon- 
ate of  potassa  a  saturated  solution  of  copper  in  1  part 
of  nitric  acid  and  3  parts  of  hydrochloric  acid,  to 
which  is  added  a  solution  of  zinc  in  concentrated 
nitric  acid.  The  light  green  precipitate  of  the  two 
carbonates  is  washed,  dried,  powdered,  and  heated  in 
a  crucible,  until  the  carbonic  acid  is  expelled,  and 
the  product  has  acquired  a  fine  greenish  hue.  This 
pigment,  misnamed  mineral  lake,  is  ground  very  fine; 
and  is  employed  for  water  and  oil  colors.  It  is  very 
durable. 

§  24.  Rinmann  green.    Cobalt  green.    Zinc  green, 

Einmann  green  is  a  combination  of  oxide  of  zinc 
with  oxide  of  cobalt.  It  is  prepared  by  dissolving  500 
grammes  of  cobalt  ore,  as  pure  as  possible,  in  4  kilo- 
grammes of  concentrated  nitric  acid,  and  adding  a 
solution  of  1  kilogramme  of  zinc  in  5  kilogrammes  of 
nitric  acid.    The  mixture  is  diluted  with  water,  and 


GREEN  COLORS. 


557 


then  precipitated  by  a  solution  of  carbonate  of  potassa. 
The  pink-white  precipitate  is  washed  upon  a  cloth, 
dried,  and  calcined  in  a  crucible  at  a  high  temperature. 
The  product  is  very  durable,  and  of  a  fine  green  color. 

Mr.  R.  Wagner,  who  has  examined  the  preparation 
of  Rinmann's  green,  expresses  himself  as  follows,  in 
a  note  published  in  the  Technologiste^  vol.  xviii.  page 
409  :— 

"  Rinmann  green,  or  cobalt  green,  is  a  color  dis- 
covered towards  the  end  of  the  last  century  by  the 
Swedish  chemist  Einmann.  It  is  obtained  by  the 
calcination  of  a  mixture  of  oxide  of  zinc  and  of  oxide 
of  cobalt.  It  is  not  so  much  on  account  of  a  want  of 
beauty  in  the  color,  as  because  the  constituent  parts 
are  expensive,  that  this  green  pigment  has  not  been 
extensively  employed.  Even  now  its  description  is 
found  only  in  chemical  books,  and  the  color  has  a 
place  only  in  collections  of  chemical  preparations. 

"  Of  late  years,  since  zinc  has  become  cheap,  and 
a  sufficiently  pure  oxide  of  cobalt  may  be  had  at  a 
moderate  price,  the  conditions  of  the  manufacture  of 
cobalt  green  are  more  favorable.  I  have,  therefore, 
undertaken  a  series  of  experiments  on  the  best  man- 
ner of  preparing  this  pigment,  and  I  will  now  give 
the  results  of  my  researches. 

"  The  first  condition,  which  is  indispensable,  is  to 
prepare  a  protoxide  of  cobalt  as  free  as  practicable 
from  foreign  metals.  For  this  purpose  the  oxide  of 
cobalt  sold  by  certain  manufacturers  of  blue  in  Sax- 
ony (Oberschlemma,  Pfannenstiel)  is  used.  It  is 
dissolved  in  3  parts  of  hydrochloric  acid,  and  the  so- 
lution is  evaporated  to  dryness.  The  residue  is  dis- 
solved again  in  6  parts  of  water,  and  a  stream  of 
sulphuretted  hydrogen  is  passed  through  the  liquor 


558 


MAOTFACTURE  OF  COLORS. 


as  long  as  precipitation  takes  place.  The  clear  liquor, 
decanted  from  the  sulphides  of  the  foreign  metals,  is 
again  evaporated  to  dryness,  and  the  residue  is  dis- 
solved in  enough  water  to  make  10  parts.  One  litre 
of  this  solution  does  not  contain  more  than  100 
grammes  of  protoxide  of  cobalt ;  therefore,  100  cubic 
centimetres  will  hold  10  grammes.  This  liquor  is 
kept  for  use. 

"If  this  solution  be  precipitated  with  the  carbon- 
ate of  soda,  and  if,  after  washing,  the  still  wet  pre- 
cipitate of  carbonate  of  protoxide  of  cobalt  be  mixed 
with  zinc  white,  there  is  produced  a  reddish-violet 
magma,  which,  after  being  dried  and  calcined,  con- 
stitutes a  green  mass,  the  color  of  which  is  the  more 
intense  in  proportion  as  the  cobalt  solution  has  been 
greater. 

"  Cobalt  green  ma}^  be  considered  as  a  mixture  of 
oxide  of  zinc  and  of  zincate  of  protoxide  of  cobalt 
(corresponding  with  the  aluminate  of  cobalt  of  the 
cobaltic  ultramarine  or  Thenard  blue).  Ammonia 
dissolves  the  oxide  of  zinc  first,  and  then  the  zinc  co- 
baltic combination,  from  the  calcined  cobalt  green. 
Melted  glass  is,  of  course,  colored  blue  by  this  pig- 
ment. If  the  cobaltic  solution  be  employed  in  such 
proportion  that,  for  one  equivalent  of  oxide  of  zinc, 
there  be  one  equivalent,  or  more,  of  protoxide  of 
cobalt,  the  calcined  pigment  will  be  a  dirty  green  or 
a  black.  The  best  tone  of  this  green  is  obtained  by 
the  combination  of  9  to  10  parts  of  oxide  of  zinc, 
with  1  to  1.5  parts  of  protoxide  of  cobalt.  But,  in 
every  case,  this  pigment  never  attains  the  brightness 
of  copper  greens,  or  even  of  ultramarine  green. 

"  Mr.  Louyet,  a  Belgian  chemist,  has  shown,  in  a 
work  on  the  preparation  of  oxide  of  cobalt  and  of 


GREEN  COLORS. 


559 


aluminate  of  protoxide  of  cobalt  in  a  pure  state,  that 
an  addition  of  phosphoric  or  of  arsenic  acid  enhances 
the  beauty  of  the  color.  If  the  addition  of  these  acids 
aids  in  the  combination  of  protoxide  of  cobalt  with 
alumina,  it  should  also  act  favorably  in  the  prepara- 
tion of  cobalt  green.  Experience  has  confirmed  this 
inference.  If  the  cobaltic  solution  be  precipitated  by 
the  phosphate  or  the  arseniate  of  potassa,  the  phos- 
phate or  the  arseniate  of  cobalt  thus  produced  pos- 
sesses the  property  of  imparting  a  green  coloration  to 
zinc  white,  at  a  temperature  much  lower  than  that 
necessary  with  the  ordinary  protoxide  of  cobalt. 
Moreover,  the  protoxide  of  cobalt  seems  to  have 
gained  more  body.  The  green  is  also  of  a  purer 
color  and  brighter.  The  alkaline  arseniates  act  like 
phosphoric  and  arsenic  acids.  If  before  the  calcina- 
tion a  small  proportion  of  arsenious  acid  be  added  to 
the  ordinary  mixture,  the  calcined  mass  will  be  of  an 
exceedingly  bright  green,  and  its  structure  being 
loosened  by  the  volatilization  of  the  arsenious  acid, 
it  will  be  easy  to  grind.  I  therefore  call  the  atten- 
tion of  those  who  may  desire  to  manufacture  cobalt 
green,  to  this  property  of  arsenious  acid,  by  which 
the  beauty  of  the  color  is  considerably  improved. 

"Since  boric (boracic)  acid  aids  the  combination  of 
the  protoxide  of  cobalt  with  the  oxide  of  zinc,  it  may 
also  possess  an  advantageous  effect;  but  I  have  not 
yet  discovered  the  best  form  in  which  it  could  be 
added  to  the  mixture.  The  borate  of  protoxide  of 
cobalt,  added  to  a  considerable  proportion  of  zinc 
white,  produces,  after  calcinatioi^  a  bluish-green; 
with  a  smaller  proportion  of  zinc,  the  mass  is  blue 
and  compact. 

"I  have  obtained  an  entirely  similar  result  by  pre- 


560 


MANUFACTURE  OP  COLORS. 


cipitating  a  solution  of  protoxide  of  cobalt  with  solu- 
ble glass  (silicate  of  soda  or  of  potassa),  mixing  the 
silicate  of  cobalt  with  zinc  white,  and  calcining. 

''The  oxide  of  antimony,  which  is  isomorphous 
with  arsenions  acid,  and  which  is  obtained  by  the 
precipitation  of  the  perchloride  of  antimony  with 
carbonate  of  soda,  has  brought  no  change  whatever 
in  the  color  of  the  cobalt  green." 

Mr.  R.  Wagner  has  made  analyses  of  Einmann 
greens  manufactured  in  Germany.  A  light  green 
sample,  from  the  technological  cabinet  of  the  Uni- 
versity of  Wtirzbourg,  was  composed  of — 

Oxide  of  zinc   88.040 

Oxide  of  iron  0.298 

Protoxide  of  cobalt  11.662 

100.000 

Other  kinds  of  green,  prepared  by  himself  a  few 
years  before,  were  finer  than  the  best  qualities  of 
copper  greens  without  arsenic.  Their  composition 
was — 

T.  II. 

Oxide  of  zine  ....  n.93  11.68 
Protoxide  of  cobalt  .  ,  .  .  19.15  18.93 
Phosphoric  acid  ....  8.22  8.29 
Soda  0.69 

Messrs.  Barruel  and  Leclaire  prepare  a  Einmann 
green,  which  they  call  zinc  green,  by  the  following 
process:  49  kilogrammes  of  dry  and  pure  sulphate 
of  cobalt  are  dissolved  in  hot  water,  and  this  solution 
is  mixed  with  245  kilogrammes  of  zinc  oxide,  pre- 
pared in  the  manner  given  in  the  paragraph  on  yel- 
low chromate  of  zinc.  The  mixture  is  dried  and 
then  calcined  at  a  clear  red  heat,  for  three  hours,  in  a 
muflae.  When  the  substance  has  cooled  off  a  little, 
it  is  thrown  into  water,  washed,  and  dried. 


GREEIT  COLORS. 


561 


Messrs.  Barruel  and  Leclaire  have  also  discovered 
another  zinc  green,  in  which  this  metal  is  combined, 
not  with  cobalt,  but  with  iron,  and  which  appears  to 
be  a  ferroso-zinc  cyanide.  The  following  is  the  mode 
of  preparation.  Prussian  blue  is  finely  powdered  and 
stirred  in  a  concentrated  solution  of  chloride  of  zinc. 
This  magma  is  put  aside  for  some  time,  and,  when  it 
has  acquired  the  desired  hue  it  is  thoroughly  washed, 
and  the  precipitate  is  dried  in  the  dark.  This  green 
is  very  handsome,  but  possesses  but  little  durability. 

§  25.  Chrome  green. 

Chrome  green  is  the  sesquioxide  of  chromium, 
which  is  prepared  in  the  arts  by  several  processes 
which  we  shall  now  describe. 

1.  The  bichromate  of  potassa  is  calcined  in  a  cru- 
cible, and  is  transformed  into  chrome  green  and  po- 
tassa, the  latter  of  which  is  washed  out. 

2.  The  bichromate  of  potassa  is  decomposed  by 
hydrochloric  acid,  when  there  is  formed  a  soluble 
chloride  of  potassium,  and  a  green  oxide  of  chromium. 

3.  A  concentrated  solution  of  bichromate  of  potassa 
is  heated,  and  while  boiling,  sublimed  sulphur  is 
added  to  it  by  small  quantities  at  a  time.  The  mix- 
ture soon  becomes  greenish,  and  the  chromic  acid  is 
transformed  into  a  gelatinous  oxide,  which  is  washed 
with  boiling  water,  dried,  and  calcined  at  a  red  heat 
in  a  crucible. 

Or,  by  the  dry  way,  an  intimate  mixture  of  equal 
parts  of  bichromate  of  potassa  and  of  sublimed  sul- 
phur is  brought  to  a  red  heat  in  a  crucible.  The 
product  is  treated  by  hot  water,  which  dissolves  the 
sulphide  of  potassium  and  the  sulphate  of  potassa 
36 


562 


MANUFACTURE  OF  COLORS. 


formed,  and  leaves  the  oxide  of  chromium  in  the 
state  of  a  green  powder,  finely  comminuted. 

4.  A  solution  of  bichromate  of  potassa  is  poufed  into 
a  neutral  solution  of  proto-nitrate  of  mercury.  There 
is  formed  an  orange  precipitate,  which  is  washed,  and 
dried  at  a  gentle  heat.  It  is  then  powdered,  and  heated 
in  a  stoneware  retort,  which  is  provided  with  an 
adapter  dipping  in  cold  water.  The  mercury  distils, 
and  is  condensed  in  the  water.  The  residue  in  the 
retort  is  a  pulverulent  oxide  of  chromium  of  a  fine  and 
dark  green. 

5.  A  mixture  of  3  parts  of  neutral  chromate  of 
potassa  and  2  of  sal  ammoniac,  is  heated  in  a  cruci- 
ble. The  two  salts  are  decomposed,  and  there  is  formed 
an  oxide  of  chromium  mixed  with  chloride  of  potas- 
sium. The  latter  salt  is  removed  by  several  washings 
of  hot  water.  A  calcination  at  a  dark-red  heat  in- 
creases the  brightness  of  the  product. 

6.  An  intimate  mixture  of  1  part  of  bichromate  of 
potassa,  and  1  of  potato  starch  (fecula),  is  calcined 
at  a  high  temperature  in  a  crucible.  The  product  is 
washed  with  boiling  water,  in  order  to  remove  the 
carbonate  of  potassa  formed,  and  a  small  proportion 
of  undecomposed  bichromate.  The  precipitated  oxide 
is  filtered,  dried,  and  calcined  again  to  remove  the 
water.  It  is  said  that  this  oxide  is  of  a  very  hand- 
some color,  and  that  it  is  easily  applied  with  the 
brush. 

Mr.  F.  Casoria,  an  Italian  chemist,  being  desirous 
of  ascertaining  the  comparative  value  of  the  first  four 
processes,  made  his  experiments  especially  in  view  of 
establishing  the  gradation  of  color  of  the  same  oxide. 

"  1.  The  first  process,  says  he,  which  I  have  tried 
twice,  and  which  is  based  upon  the  decomposition  of 


GREEN  COLORS. 


563 


chromate  of  mercury,  gave  me  a  very  comminuted 
material,  of  a  dark-green  color. 

"2.  'The  sesquioxide  of  chromium,  precipitated 
from  a  solution  of  chloride  of  chromium  by  ammonia, 
is  a  green  between  a  gray  and  a  blue. 

"3.  The  oxide  of  chromium,  resulting  from  the 
decomposition  of  the  bichromate  of  potassa  alone,  at 
a  very  high  heat,  is  of  a  dark-green  color  and  very 
compact.  Its  hue  resembles  that  of  the  oxide  obtained 
by  the  calcination  of  the  chromate  of  mercury. 

"4.  Lastly,  the  decomposition  of  the  bichromate 
of  potassa  by  sulphur,  has  furnished  a  dense  oxide  of 
an  intense  green  color. 

"For  my  own  satisfaction  I  have  tried  other  pro- 
cesses, which  gave  me  less  satisfactory  results." 

§  26.  Emerald  green. 

Emerald  green  is  another  sesquioxide  of  chromium,  \  / 
prepared  in  a  particular  manner. 

There  has  been  in  the  trade  for  a  long  time,  under 
the  names  of  emerald  green  and  Pannetier  green,  a 
handsome  and  durable  color  which  was  sold  at  a  high 
price.  The  inventor,  Mr.  Pannetier,  has  not  published 
his  process,  but  communicated  it  to  Mr.  Binet  alone, 
as  an  acknowledgment  of  the  aid  given  by  the  latter 
person,  in  putting  his  pottery  kilns  at  his  disposal. 
All  that  is  known  of  this  secret  composition,  is  that 
the  green  is  a  chromium  compound,  prepared  in  the 
dry  way.  A  few  experimenters  have  also  said  that 
they  had  found  boric  (boracic)  acid  in  it. 

The  remarkable  researches  of  Ebelmen  upon  the 
artificial  production  of  mineral  compounds  have  shown 
the  advantages  which  may  be  had  from  boric  acid  as 


564 


MANUFACTURE  OF  COLORS. 


a  solvent.  At  a  high  temperature,  boric  acid  acts 
like  a  solvent,  water  for  instance,  and  forms  combina- 
tions more  or  less  stable  with  the  dissolved  substance. 
The  latter  may  be  separated  from  the  boric  acid,  either 
by  a  higher  temperature,  which  volatilizes  the  acid, 
or  by  solution  in  water,  alcohol,  etc. 

Ebelmen,  when  using  boracic  acid,  employed  the 
method  of  volatilization.  Mr.  Guignet  uses  it  also 
as  a  flux ;  but,  instead  of  removing  it  by  a  high  teai- 
perature,  he  dissolves  it  in  water.  The  following  is 
a  resume  of  the  mode  of  operation  of  Mr.  Guignet. 

This  color  may  be  prepared  by  two  processes : — 

First  process. — There  is  heated,  upon  the  bed  of  a 
reverberatory  furnace  brought  to  a  dark-red  heat,  a 
mixture  of  1  part  of  bichromate  of  potassa  and  3  parts 
of  boric  acid,  moistened  with  enough  water  to  make 
a  thick  paste.*  The  product,  while  red  hot,  is  thrown 
into  cold  water,  and  washed  with  boiling  water,  in 
order  to  remove  the  borate  of  potassa.  The  hydrated 
oxide  of  chlorium  is  dried  or  kept  in  the  pasty  state. 
By  evaporating  the  liquors,  and  adding  hydrochloric 
acid,  the  greater  part  of  the  boracic  acid  is  recovered. 

Second  process. — The  bichromate  of  potassa  of  the 
first  process  is  replaced  by  an  equal  quantity  of  chro- 
mate  of  soda,  which  is  prepared  by  dissolving  in  boil- 
ing water  61  parts  of  neutral  chromate  of  potassa,  and 
53  parts  of  nitrate  of  soda.  The  neutral  chromate  of 
potassa  may  also  be  replaced  by  a  mixture  of  92  parts 
of  bichromate  of  potassa,  and  89  parts  of  crystallized 
carbonate  of  soda,  and  the  indicated  proportion  of 

*  The  temperature  should  not  be  above  a  dark-red  heat,  other- 
wise the  substance  will  fuse  entirely,  instead  of  forming  a  porous 
mass.  The  oxide  will  become  anhydrous,  the  color  of  which  is  a 
pale  green. 


GREEN^  COLORS. 


565 


nitrate  of  soda  remains  as  before.  In  either  case,  the 
solution,  in  cooling,  deposits  a  quantity  of  nitrate  of 
potassa  (saltpetre),  which  pays  one  part  of  the  ex- 
penses. The  mother  liquors  contain  the  chromate  of 
soda,  which  may  be  crystallized ;  or,  what  is  prefer- 
able in  this  case,  the  liquors  are  evaporated  to  dryness, 
and  the  residue  will  be  a  sufficiently  pure  chromate 
of  soda,  provided  all  the  nitrate  of  potassa  has  been 
separated. 

By  the  second  process  of  preparation  of  the  chro- 
mate of  soda,  the  indicated  proportions  give  twice  as 
much  of  chromate  of  soda  as  in  the  former  case. 

When  the  green  color  is  manufactured  with  the 
chromate  of  soda,  the  liquors  contain  borax,  which 
may  be  sold  directly  as  such  or  converted  into  boric 
acid  by  the  addition  of  hydrochloric  acid.  The  color 
prepared  from  the  chromate  of  soda  is  of  a  lighter 
green  than  that  produced  by  the  bichromate  of  potassa. 
Still  lighter  colored  pigments  may  be  obtained  by  add- 
ing to  the  mixture  of  bichromate  and  of  boric  acid, 
before  calcination,  a  certain  proportion  of  alumina, 
magnesia,  blanc  fixe,  etc. 

The  chromates  of  potassa  or  soda  may  also  be 
replaced  by  the  chromate  of  lime,  obtained  by  the 
direct  calcination  of  chromic  iron  and  chalk,  in  an 
oxidizing  flame. 

"  Although  the  first  process  appears  very  simple,  it 
is  however  necessary,  says  Mr.  Casoria,  to  indicate  a 
few  precautions,  which,  if  they  were  neglected,  would 
result  in  an  inferior  product.  The  first  condition  is 
to  avoid  an  excess  of  heat,  and  the  best  temperature 
is  that  below  a  red  heat.  If  it  be  attempted  to  de- 
compose entirely  the  bichromate  of  potassa  by  an 
increase  of  temperature,  the  colored  precipitate  will 


566 


MANUFACTUHE  OF  COLORS. 


be  abundant,  but  of  a  dirty  green.  The  very  large 
proportion  of  boracic  acid  has  a  manifest  influence  on 
the  color  of  the  oxide,  as  I  have  repeatedly  ascer- 
tained by  direct  experiments." 

In  regard  to  the  economy  of  the  process,  we  should 
notice  that  the  first  washings  deposit,  in  cooling,  a 
large  proportion  of  boric  acid,  and  contain  a  certain 
proportion  of  borate  of  potassa  and  of  undecomposed 
bichromate  of  potassa.  It  is  not  necessary  to  demon- 
strate that  these  two  residua  of  the  process  may  be 
used  quite  ad  infinitum  in  the  subsequent  operations. 
Thus  it  is  that  a  certain  quantity  of  boric  acid  is 
sufficient  for  many  operations. 

This  process  may  be  tried  with  a  very  small  quan- 
tity of  materials,  in  a  platinum  dish,  and  over  an 
alcohol  lamp.  The  calcined  substance,  thrown  into 
boiling  water,  deposits  a  green  precipitate,  which 
may  be  mistaken  for  the  finest  quality  of  Scheele's 
green. 

Mr.  Arnaudon  has  proposed  in  the  Technologiste, 
vol.  XX.  p.  519,  a  diflerent  process  for  the  preparation 
of  an  oxide  of  chromium,  equal  in  color  to  the  finest 
Schweinfurt  green.    The  following  is  his  process:— 

Take  the  equivalent  weights  of  the  following  salts: — 

Neutral  phosphate  of  ammonia  (crystallized)    128  parts 
Bichromate  of  potassa  149  " 

and  mix  them  thoroughly,  either  by  grinding,  or  by 
dissolving  them  in  a  minimum  of  hot  water,  and 
exaporating  the  solution  to  the  consistency  of  a 
magma,  which  becomes  hard  by  cooling.  This  mass 
is  broken  into  small  pieces,  which  are  heated  in  a 
shallow  dish  at  the  temperature  of  170°  to  180°  C. 
At  that  temperature  the  mixture  becomes  soft,  then 


GREE^^"  COLORS. 


567 


pasty,  and  soon  intumesces,  changes  its  color,  and 
disengages  a  small  proportion  of  water  and  ammonia. 
The  heat  is  continned  for  about  half  an  hour,  without 
going  above  200°  C.  Beyond  that  point,  for  in- 
stance at  the  temperature  necessary  for  the  produc- 
tion of  Guignet's  emerald  green,  the  green  coloration 
of  the  mixture  disappears,  and  is  replaced  by  a  dark 
brown  color  due  to  binoxide  of  chromium.  By 
raising  the  temperature  still  higher,  at  a  brown-red 
heat  for  instance,  the  former  color  changes  to  a  blue, 
which  is  durable  in  presence  of  water.  If  the  tem- 
perature be  maintained  at  that  point,  when  the  mix- 
ture has  become  green,  and  if  the  product  be  washed 
with  hot  water,  to  remove  the  soluble  salts,  there 
will  be  obtained  a  nearly  impalpable  powder  of  oxide 
of  chrome,  the  color  of  which  resembles  that  of  new 
leaves,  and  forms  a  near  approach  to  the  green  of  the 
first  chromatic  circle  of  Mr.  Chevreul. 

The  green  obtained  by  this  process,  freed  from 
soluble  salts  by  washings  in  hot  water,  dried  at  160°  C, 
and  brought  to  a  red  heat  in  a  tube,  gives  off  water, 
and  does  not  become  dark  like  the  bihydrate  of  MM. 
Guignet  and  Salvetat.  While  hot,  it  is  of  a  violet- 
red  color,  which  passes  to  a  gray,^  and,  lastly,  to  a 
green  when  entirely  cold.  However,  the  hue  is  different 
from  that  presented  by  the  green  before  its  calcina- 
tion ;  and  by  operating  with  care,  a  green  of  anhy- 
drous sesquioxide  of  chromium  may  be  obtained, 
which  rivals  that  of  Schweinfurt.  Mr.  Arnaudon  is 
not  positive  in  regard  to  the  composition  of  this 
green,  because,  notwithstanding  repeated  washings, 

*  This  gray  coloration  is  due  to  less  red  and  more  green,  which 
complementary  colors,  by  their  combination,  produce  black. 


568 


MANUFACTURE  OP  COLORS. 


it  will  still  show  the  presence  of  phosphoric  acid  after 
a  fusion  with  a  mixture  of  nitrate  and  carbonate  of 
potassa.  The  proportions  obtained  do  not  allow  of 
a  certain  decision  as  to  whether  this  acid  is  combined 
in  definite  proportions,  or  simply  held  by  what  Mr. 
Chevreul  calls  capillary  affinity ;  that  is  to  say,  by 
an  affinity  analogous  to  that  of  tannin  for  leather,  or 
of  coloring  substances  for  tissues. 

Mr.  Arnaudon,  disregarding  the  fact  of  the  traces 
of  phosphoric  acid  obtained,  has  found  that  this  ses- 
qui oxide  of  chromium  contains  about  11.70  per  cent, 
of  water,  which  corresponds  to  the  monohydrate  of 
sesquioxide  of  chromium  Cr^OlHO. 

This  chrome  green  is  remarkable  for  its  property 
of  preserving  its  brightness  and  purity  under  arti- 
ficial light.  It  resists  acids,  alkalies,  and  sulphuretted 
hydrogen.  The  colors  resulting  from  its  mixture 
with  other  pigments  are  not  altered,  and  it  is  not 
poisonous.  On  account  of  all  these  advantages,  it  is 
to  be  desired  that  painters  should  employ  it  in  their 
works.  Indeed,  if  their  pallets  were  entirely  composed 
of  colors  as  durable  as  this  one,  their  chefs  d'oeuvre 
would  pass  unaltered  through  ages,  and  with  less 
danger  of  being  disfigured  by  unskilful  restorations. 

This  pigment  may  also  be  used  for  calico-printing 
with  albumen,  etc. 

§  27.  Titanium  green, 

Mr.  L.  Eisner  has  proposed  to  prepare  with  titanium 
a  green  color  without  arsenic  or  copper.  The  follow- 
ing is  the  process  described  by  this  chemist : — 

Several  years  ago,  says  Mr.  Eisner,  Lampadius 
had  published  a  few  experiments  he  made  for  the  pur- 


GREEN  COLORS. 


569 


pose  of  preparing  a  dark  green  color  from  rutile.* 
He  melted  at  a  red  heat,  in  a  Hessian  crucible,  500 
parts  of  powdered  rutile,  and  1500  parts  of  purified 
potassa.  The  melted  mass  was  saturated  with  hydro- 
chloric acid,  then  filtered,  and  the  clear  liquor  was 
precipitated  with  a  solution  of  ferrocyanide  of  po- 
tassium. The  precipitate,  washed  and  dried,  was 
titanium  green.  With  500  parts  of  rutile,  Lampadius 
obtained  855  parts  of  green.  The  preparation  of  tita- 
nium green,  either  from  washed  rutile  or  iserine,  has 
been  found  more  advantageous  by  the  following  pro- 
cess : — 

The  clean  ore  is  melted  with  twelve  times  its  weight 
of  acid  sulphate  of  potassa  in  a  Hessian  crucible.  After 
cooling,  the  melted  mass  is  powdered,  and  digested 
until  it  is  dissolved  in  hydrochloric  acid  diluted  with 
50  per  cent,  of  water,  maintained  at  the  temperature 
of  50°  C.  The  hot  solution  is  separated  from  the  in- 
soluble residue  by  filtration,  and  the  filtrate  is  evapo- 
rated until  a  drop  of  the  liquor,  put  upon  a  piece  of 
glass  or  porcelain,  becomes  of  the  consistency  of  a 
magma.  The  whole  is  allowed  to  cool  ofi"  in  the 
porcelain  dish,  and  the  magma,  composed  of  nearly 
pure  titanic  acid,  is  thrown  upon  a  filter.  The  drain- 
ings  are  again  evaporated,  and  furnish  a  new  portion 
of  titanic  acid.  When  the  magma  has  been  suffi- 
ciently drained,  it  is  mixed  with  a  large  volume  of 
water,  holding  a  small  proportion  of  ammonia,  in 
order  to  prevent  the  formation  of  a  basic  salt  of  iron. 
This  liquor  is  kept  boiling  for  a  long  time,  and  the 

*  Rutile  is  titanic  acid  mixed  with  a  greater  or  less  proportion 
of  the  oxides  of  iron  and  manganese,  and  sometimes  of  oxide  of 
chromium.  Iserine  or  nigrine  is  a  combination  of  titanic  acid 
with  oxide  of  iron,  and  a  few  other  substances. 


570 


MANUFACTURE  OF  COLORS. 


precipitated  titanic  acid,  after  filtration  and  washings, 
is  nearly  white.  After  several  similar  treatments 
with  the  bisulphate  of  potassa,  it  may  be  obtained 
entirely  free  from  iron. 

As  i serine  contains  generally  some  carbonate  of 
lime,  it  is  advisable  to  digest  it  with  dilute  hydro- 
chloric acid,  before  it  is  treated  with  the  acid  sulphate 
of  potassa. 

A  concentrated  solution  of  sal  ammoniac  is  poured 
upon  the  magma,  prepared  in  the  manner  explained 
above,  and,  after  a  thorough  mixing,  it  is  filtered.  The 
titanic  acid  remaining  upon  the  filter  is  digested  in 
diluted  hydrochloric  acid,  and  kept  at  a  temperature 
of  50°  to  60°  C,  until  the  solution  is  as  complete  as 
practicable.  The  acid  liquor,  after  the  addition  of 
ferrocyanide  of  potassium,  is  rapidly  brought  to  a 
boil,  and  there  is  formed  a  precipitate  of  a  handsome 
titanium  green,  which  is  washed  with  water  holding 
a  small  proportion  of  hydrochloric  acid.  The  solu- 
tion of  titanic  acid  must  be  very  acid,  because  if  pure 
water  be  employed,  and  the  ferrocyanide  poured  upon 
the  magma,  the  precipitate  will  be  a  yellowish-brown 
becoming  green  by  ebullition  in  dilute  hydrochloric 
acid.  The  green  precipitate  becomes  white  with 
ammonia.  The  liquor,  filtered  from  the  green  pre- 
cipitate, still  contains  a  certain  quantity  of  titanic 
acid,  which  ammonia  will  separate  in  the  shape  of  a 
white  flocculent  precipitate. 

The  dry  titanium  green,  obtained  either  from  rutile 
or  iserine,  is  a  dark-green  powder.  It  is  decomposed 
at  the  temperature  of  100°  C.  Its  desiccation  should 
therefore  be  carefully  conducted. 

By  this  method,  iserine  and  any  titaniferous  iron- 
ore  will  produce  a  green  as  handsome  as  that  pre- 


GREEI^  COLORS. 


571 


pared  from  rutile.  Moreover,  the  liquor  holding  the 
double  sulphate  of  iron  and  potassa  will  give  a 
Prussian  blue  by  the  addition  of  ferrocyanide  of 
potassium.  Therefore,  this  method  will  allow  of  the 
manufacture,  with  iserine,  of  titanic  acid,  titanium 
green,  and  Prussian  blue. 

§  28.  Green  ochire, 

Mr.  Bouland,  of  Orleans,  has  composed  a  color, 
called  green  ochre,  by  the  following  formula:  50 
kilogrammes  of  dry  ochre,  in  powder,  are  mixed  into 
a  paste  with  water  and  1  kilogramme  of  hydrochloric 
acid.  Twenty-four  hours  after,  1  kilogramme  of  yel- 
low prussiate  of  potassa  is  also  thoroughly  mixed 
with  the  above  paste.  Lastly,  an  aqueous  solution 
of  j)ersulphate  of  iron  is  added  in  order  to  arrive  at  a 
given  hue. 

A  great  variety  of  hues  may  be  obtained  by 
changing  the  proportions  of  yellow  prussiate.  This 
green  is  used  in  the  manufacture  of  paper-hangings. 

§  29.  Green  iiUramarine. 

This  is  a  light  bluish-green,  having  a  composition 
similar  to  that  of  blue  ultramarine ;  that  is,  it  con- 
tains sulphur,  silica,  alumina,  soda,  with  traces  of 
iron  and  lime.  The  difference  appears  to  be  a  greater 
proportion  of  sulphur  in  the  green  ultramarine.  In- 
deed, with  the  same  temperature,  if  air  be  allowed  to 
come  in  contact  with  the  crucibles  containing  the 
ultramarine,  this  substance  will  be  blue.  On  the 
other  hand,  if  air  does  not  intervene  for  burning  the 
excess  of  sulphur,  the  ultramarine  will  be  green,  but 
will  pass  to  a  blue  by  a  calcination  in  the  air. 

Green  ultramarine  possesses  a  certain  brightness 


572 


MANUFACTURE  OF  COLORS. 


under  artificial  light,  resists  sulphuretted  hydrogen, 
and  is  not  readily  attacked  by  alkalies  ;  but  the  weak- 
'  est  acids  decompose  it  with  production  of  sulphuretted 
hydrogen.  Mixed  with  other  colors,  or  ground  with 
oils,  gums,  or  varnishes,  it  is  altered  if  these  sub- 
stances be  acid,  or  will  develop  acidity. 

§  30.  Verdigris, 

Eecent  researches  have  shown  that  verdigris  is  a 
basic  hydrated  acetate  of  copper,  composed  of  variable 
proportions  of  bibasic  and  tribasic  acetates  of  copper. 
We  shall  not  tarry  on  the  manufacture  of  this  color, 
which  was  known  to  the  painters  of  antiquity,  and 
which  forms  a  special  trade  in  certain  localities. 

Verdigris  is  manufactured  in  France,  in  the  depart- 
ments of  Aude  and  Herault,  by  oxidizing  pieces  of 
old  sheet  copper  from  2  to  3  millimetres  thick,  heated 
to  80°  C,  with  a  solution  of  acetate  of  copper,  and 
then  immersing  them  in  the  skins  of  pressed  grapes, 
which  are  in  a  state  of  acetic  fermentation.  After  a 
certain  length  of  time,  which  is  indicated  by  experi- 
ence and  various  phenomena,  the  copper  plates  are 
removed  from  the  skins,  dried  in  the  air,  then  dipped 
into  water,  and  again  laid  in  layers  of  grape  skins. 
When  this  operation  has  been  repeated  five,  six,  or 
seven  times,  the  verdigris  has  acquired  a  thickness 
of  from  2  to  3  millimetres,  and  is  scraped  off,  then 
kneaded  in  wooden  troughs,  and  packed  in  leather 
bags.    Its  desiccation  is  completed  in  the  air. 

Yerdigris  is  also  prepared  by  covering  copper 
plates  with  vinegar. 

Verdigris  is  of  a  pure  green,  or  of  a  bluish-green, 
according  to  the  proportion  of  sesquibasic  acetate  it 
contains.    When  it  is  pure  it  is  entirely  dissolved, 


GREEN  COLORS. 


573 


and  without  effervescence,  in  diluted  nitric  and  sul- 
phuric acids.  It  is  highly  poisonous,  and  is  not  a 
durable  color. 

§  31.  Crystallized  verdet    Distilled  green.  Crystals 

of  Venus. 

Verdet  is  a  neutral  acetate  of  copper  which  is 
manufactured  in  the  south  of  France.  This  salt  is 
of  a  fine  green  color,  its  taste  is  sweet  and  styptic  at 
the  same  time,  and  it  is  soluble  in  water  and  alcohol. 
Its  crystals  form  very  regular  rhombs,  of  a  very  dark 
green.  It  is  decomposed  by  heat,  and  the  distilled 
acid  produced  is  colored  by  a  small  quantity  of  oxide 
carried  away  mechanically.  According  to  Yogel,  a 
small  proportion  of  anhydrous  acid  is  sublimed  at 
the  same  time  in  the  shape  of  white  silky  crystals. 

This  acetate  of  copper  is  prepared  by  dissolving 
verdigris  in  vinegar,  filtering  the  solution,  and  letting 
it  crystallize. 

This  salt  is  employed  for  water-color  painting.  It 
is  very  poisonous,  and  the  green  coating  deposited 
upon  copper  vessels  is  still  more  dangerous. 

The  verdet  may  be  obtained  by  double  decompo- 
sition, and,  indeed,  this  is  the  process  generally  fol- 
lowed in  the  factories  where  acetic  acid  is  prepared 
from  distilled  wood.  A  solution  of  100  kilogrammes 
of  acetate  of  lime  is  decomposed  by  one  of  140  kilo- 
grammes of  sulphate  of  copper;  there  results  an 
insoluble  sulphate  of  lime,  and  a  solution  of  acetate 
of  copper,  which  is  decanted,  evaporated,  and  crys- 
tallized. 

The  liquor  known  under  the  name  of  water-green^ 
and  used  as  a  water-color,  is  prepared  by  dissolving 
the  most  colored  crystals  of  verdet  in  a  slightly 
alkaline  water. 


574 


MANUFACTURE  OF  COLORS. 


SECTION  YII. 

COLORS  PROM  SULPHATE  OF  ZINC. 

We  shall  close  our  remarks  on  colors  by  describing 
a  process  for  the  preparation  of  colors  with  the  oxide 
of  zinc,  which  has  been  proposed  by  Messrs.  L.  Ador 
&  E.  Abadie. 

"  The  oxide  of  zinc,  which  forms  the  basis  of  this 
manufacture,  is  obtained  by  the  decomposition  of  the 
salts  of  this  metal  by  heat,  either  in  furnaces  or  in 
retorts.  The  advantage  of  these  colors  is  their  salubrity 
and  their  economy.  When  the  oxide  derives  from  de- 
composed sulphates,  monohydrated  sulphuric  (ISTord- 
hausen)  acid  is  disengaged,  and  the  remaining  oxide, 
by  its  combination  with  other  metallic  oxides,  forms 
all  the  colors,  hues,  and  tones  which  may  be  desired. 

"The  sulphate  of  zinc  is  prepared  as  follows: 
Metallic  zinc  is  dissolved  in  sulphuric  acid  marking 
18°  to  20°  Be.  When  the  saturation  is  complete,  the 
liquor  is  left  to  stand  until  it  is  clear,  and  it  marks 
then  36°  to  38°  Be.  The  liquor  is  then  evaporated 
in  leaden  vessels  until  it  forms  a  pasty  mass,  which 
is  spread  and  cooled  upon  zinc  or  lead  plates.  The 
salt  is  broken  as  finely  as  practicable  with  a  wooden 
spatula. 

"The  mixtures  of  metallic  salts  forming  with  sul- 
phate of  zinc  various  colors,  are  as  follows : — 

"Delicate  light  yellows,  called  Roman  yellows. — 
They  are  obtained  by  a  simple  decomposition  by 
heat  of  the  sulphate  of  zinc  in  retorts  and  in  furnaces. 

''Chamois  yellows. — 100  parts  of  sulphate  of  zinc 
in  solution,  are  mixed  with  li  parts  of  a  solution  of 
sulphate  of  iron  marking  28°  to  30°  Be. 

"Yellow  chamois. — 100  parts  of  sulphate  of  zinc  in 


ZINO  COLORS. 


575 


solution,  are  mixed  with  2|  parts  of  a  solution  of 
sulphate  of  iron  marking  from  28°  to  30°  Be. 

''Dark  chamois, — The  proportion  of  iron  solution 
is  increased  to  suit  the  hue  desired. 

''Gold  yellows. — 100  parts  of  sulphate  of  zinc  in 
solution  are  mixed  with  2|  parts  of  a  solution  of 
nitrate  of  manganese  marking  12°  to  14°  Be. 

"  Dark  gold  yellows. — The  proportion  of  nitrate  of 
manganese  is  increased  to  suit. 

"Greens  resembling  Scheele's  greens. — 100  parts  of 
sulphate  of  zinc,  in  solution,  are  mixed  with  2^  parts 
of  a  solution  of  nitrate  of  cobalt  marking  20°  Be. 

"  Dark  greens. — The  proportion  of  nitrate  of  cobalt 
is  increased. 

"  Yellowish  greens, — 100  parts  of  sulphate  of  zinc 
are  mixed  with  2|  parts  of  a  solution  of  nitrate  of 
nickel,  at  16°  Be.,  and  a  few  drops  of  a  solution  of 
nitrate  of  silver. 

"Grays. — 100  parts  of  sulphate  of  zinc  in  solution, 
are  mixed  with  2J  parts  of  a  solution  of  sulphate  of 
copper. 

"Bronzes. — 100  parts  of  sulphate  of  zinc  are  mixed 
with  3  parts  of  a  solution  of  nitrate  of  nickel  at  15° 
to  16°  Be.,  3  parts  of  a  solution  of  nitrate  of  cobalt 
of  the  same  specific  gravity,  and  from  1  to  1|  per 
cent,  of  a  solution  of  nitrate  of  copper  of  the  same 
specific  gravity. 

"Dark  bronzes. — The  same  materials  are  employed, 
in  the  same  proportions,  but  they  are  calcined  longer. 

"Pinks. — 100  parts  of  sulphate  of  zinc  in  solution, 
are  mixed  with  2  to  3  parts  of  a  solution  of  nitrate 
of  iron  marking  20°  to  25°  Be. 

"Dark  pinks, — The  proportion  of  nitrate  of  iron  is 
increased. 


576 


MANUFACTURE  OF  COLORS. 


"  Whites, — They  are  obtained  by  employing  a  sul- 
phate of  zinc  very  pure,  especially  free  from  iron, 
which  is  tested  with  the  sulphocyanide  of  potassium. 
The  greatest  care  should  be  taken  to  employ  clean 
drying  vessels,  and  the  cooling  of  the  sulphate  should 
be  made  in  stoneware  pots. 

"The  various  combinations  of  materials,  and  the 
chemical  reactions  which  produce  these  colors,  require 
a  variable  length  of  time  for  the  transformations  to 
be  completed,  according  to  the  apparatus  employed, 
the  temperature,  and  the  colors  or  hues  desired.  The 
operation  requires  to  be  watched  attentively,  and  the 
fire  should  be  removed  as  soon  as  the  given  hue  or 
tone  is  obtained. 

"  The  sulphate  of  zinc,  mixed  with  the  other  solutions 
of  coloring  oxides,  is  reduced  to  a  thick  paste,  which 
is  introduced  into  a  furnace  or  into  a  retort.  Th^ 
calcination  lasts  from  four  to  eight  hours  in  retorts, 
and  about  one-half  of  this  time  in  reverberatory  fur- 
naces. Side  openings  allow  of  the  watching  of  the 
operation  in  the  furnace,  and  of  the  extraction  of  the 
materials  when  the  desired  hue  has  been  obtained. 

"The  colored  oxides  of  zinc,  after  their  removal 
from  the  retorts  or  furnaces,  are  pulverized  in  conical 
mills  or  under  stones,  and  then  more  finely  ground 
and  sifted. 

"  The  nitrates,  chlorides,  and  acetates  of  zinc  pro- 
duce similar  results  when  they  are  treated  in  the  same 
manner  with  the  same  metallic  salts.  Every  kind  of 
color  may  also  be  prepared  by  calcining  carbonate  of 
zinc  with  the  carbonates  of  the  coloring  metals ;  but, 
instead  of  working  them  by  the  wet  way,  they  are 
employed  in  powder  and  treated  by  the  dry  method. 
It  is  necessary  that  the  carbonates  of  zinc,  iron, 


DRYING  AND  ADHERENCE  OF  COLORS.  577 

copper,  cobalt,  antimony,  manganese,  bismuth,  nickel, 
etc.,  should  be  very  pure. 

"  The  proportion  of  the  coloring  carbonates  should 
not  be  less  than  6  per  cent,  of  the  weight  of  the  car- 
bonate of  zinc,  and  the  amount  is  increased  according 
to  the  hue  desired. 

"The  operation  requires  two  or  three  hours  of 
calcination.  When  the  color  and  the  hue  have  been 
obtained,  the  substances  are  removed  from  the 
furnace,  ground,  and  sifted  in  the  afore-mentioned 
manner." 


CHAPTEK  III. 

DRYING  AND  ADHERENCE  OY  COLORS. 

A  VERY  important  question  in  applying  colors  is 
the  facility  with  which  they  dry,  when  they  have 
been  ground  with  water,  essential  or  fixed  oils,  or 
varnishes.  Indeed,  it  is  necessary  that  these  paints 
should  rapidly  acquire  a  certain  degree  of  desiccation 
in  order  that  the  places  where  they  have  been  applied 
may  be  inhabited,  and  also  for  the  purpose  of  render- 
ing them  resisting  to  friction.  Until  recently,  colors 
were  made  drying  by  the  single  process  of  mixing 
them  with  oil  boiled  with  litharge ;  but  chemistry 
has  caused  improvements  to  be  introduced  into  this 
part  of  the  painter's  art,  on  which  it  will  be  useful 
for  us  to  tarry  a  little  while. 
37 


578 


MANUFACTURE  OF  COLORS. 


SECTION  I. 

DRYER  FOR  ZINC  WHITE. 

The  colors  prepared  with  zinc  white  dry  more 
slowly  than  those  of  white  lead.  Mr.  Led  aire  has 
therefore  searched  for  a  dryer  more  powerful  than 
litharge,  and  has  ascertained  that  the  j^eroxide  of 
manganese  is  preferable  to  all  the  other  metallic 
oxides.    The  following  is  his  process  : — 

Purified  linseed  oil  is  boiled  for  6  or  8  hours,  and 
to  every  100  kilogrammes  of  boiled  oil  there  are 
added  5  kilogrammes  of  powdered  peroxide  of  man- 
ganese, which  may  be  kept  in  a  bag,  like  litharge. 
The  liquid  is  boiled  and  stirred  for  5  or  6  hours  more, 
and  then  cooled  and  filtered. 

This  drying  oil  is  employed  in  the  proportion  of  5 
to  10  per  cent,  of  the  weight  of  zinc  white,  and  it  is 
better  to  add  it  during  the  grinding  of  the  pigment 
in  oil,  since  the  mixture  is  more  thorough. 

SECTION  II. 

DRYING  OILS. 

Mr.  Leclaire  has  not  confined  himself  to  the  above 
process  for  oxidizing  oils,  but  he  has  also  searched 
for  a  mode  of  rendering  them  thicker,  and  indicates 
the  following  method  : — 

Oil  oxygenized  (oxidized)  by  the  peroxide  of  man- 
ganese, says  he,  may  be  thickened  to  the  point  of 
becoming  solid,  when  it  will  produce  the  same  effects 
as  litharge. 

Fifteen  parts  of  lime,  made  into  paste  with  water, 
are  added  to  100  parts  of  oil  oxidized  by  the  per- 
oxide of  manganese.    The  whole  is  boiled,  or  heated 


DRYING  AND  ADHERENCE  OF  COLORS.  579 


by  steam,  until  the  water  has  evaporated ;  the  oil 
forms  then  with  lime  a  thick  product  which  is  a 
dryer.  It  is  sold  in  lumps,  or  in  powder,  or  ground 
with  an  equal  weight  yf  oxidized  oil.  It  may  be 
ground  with  the  ordinary  essence  of  turpentine,  or 
with  that  of  Venice,  but  the  dryer  is  less  powerful 
than  when  it  has  been  mixed  with  oxidized  linseed 
oil.  Three  to  five  per  cent,  of  this  dryer  are  sufiicient 
for  a  rapid  desiccation. 

Other  dryers  may  be  made  by  combining  lime  with 
resins  and  essences  of  turpentine,  in  the  proportions 
indicated  for  fixed  oils. 

SECTION  III. 

POWDERED  DRYER  OP  GUYNEMER. 

For  a  long  time,  says  Mr.  Guynemer  in  a  patent 
taken  out  for  this  purpose,  it  has  been  a  desideratum 
to  find  an  impalpable  white  powder  which  may  be 
intimately  incorporated  with  zinc  white,  and  which 
will  accelerate  its  desiccation. 

The  use  of  litharge  and  acetate  of  lead,  as  dryers, 
is  open  to  the  inconvenience  of  diminishing  the 
unalterability  and  innocuity  of  zinc  white;  and  on 
this  account,  Mr.  Leclaire  has  proposed  for  zinc 
white  an  oil  rendered  drying  by  manganese. 

The  employment  of  these  oils  is  sometimes  diffi- 
cult, because  their  preparation  is  not  well  understood 
everywhere,  and  because  the  expenses  of  transporta- 
tion, the  leakage,  and  the  duties  are  heavy.  It  hap- 
pens, also,  in  certain  cases,  that  the  brightness  of 
the  pigment  is  impaired. 

Mr.  Leclaire,  in  his  patents,  claims  the  mode  of 


580 


MANUFACTURE  OF  COLORS. 


rendering  oils  drying,  and  the  use  of  all  the  combi- 
nations of  manganese  as  dryers. 

The  Society  of  the  Yieille-Montagne,  represented 
by  Mr.  Guynemer,  has  become  the  owner  of  the 
patents  of  Mr.  Leclaire,  and  the  following  formula  is 
a  new  manganese  dryer,  in  powder : — 

Take — Pure  sulphate  of  manganese  .  .*  .1  part 

Pure  acetate  of  manganese    .  .  .      1  " 

Calcined  sulphate  of  zinc      .  .  .      1  " 

White  oxide  of  zinc       .       .  .  .97  parts. 

100 

The  sulphates  and  the  acetate  are  ground  in  a 
mortar  to  an  impalpable  powder,  which  is  passed 
through  a  metallic  sieve. 

Three  parts  of  this  powder  are  dusted  over  the  97 
parts  of  oxide  of  zinc,  spread  over  a  board  or  a 
slab.  The  whole  is  then  thoroughly  mixed  and 
ground. 

The  resulting  white  and  impalpable  powder,  mixed 
in  the  proportion  of  |  to  1  per  cent,  with  zinc  white, 
will  enormously  increase  the  drying  property  of  this 
product,  which  will  become  dry  in  10  to  12  hours. 

SECTION  lY. 

VARIOUS  DRYERS.     ZUMATIC  DRYER. 

Mr.  Zienkowicz  is  the  chemist  who  appears  to  us, 
in  a  patent  described  Vol.  xxiv.  p.  319  of  the  Itecueil 
des  Brevets  Invention^  to  have  investigated  the  ques- 
tion of  dryers  for  painting  the  most  thoroughly. 

"We  reproduce  here  an  extract  from  this  work  on 
the  preparation  of  the  zumatic  dryer. 

"Since  it  has  been  tried  to  substitute  zinc  oxide 
for  white  lead  in  painting,  it  is  natural  that  researches 


DRYIJiTG  AND  ADHERENCE  OF  COLORS.  581 

should  also  have  been  made  to  replace  litharge,  as  a 
dryer,  by  a  substance  free  from  the  inconveniences 
which  caused  the  abandonment  of  white  lead.  In- 
deed, if  sulphuretted  hydrogen  impairs  the  whiteness 
of  the  painting  done  with  white  lead,  it  is  not  logical 
to  employ  a  lead  dryer  with  zinc  paints,  because  the 
latter  substances  will  lose  their  advantages  of  not  be- 
coming dark  like  white  lead. 

"It  has  been  known  for  a  long  time,  that  several 
metallic  oxides  and  salts,  especially  the  sulphate  of 
zinc,  umber,  and  the  oxide  of  manganese,  have  the 
property  of  combining  with  oils,  which  they  render 
drying.  But  oxide  of  lead  having  been  found  to  pos- 
sess the  greatest  action  upon  oils,  it  has  been  pre- 
ferred to  the  others,  up  to  the  present  time,  since  its 
employment  in  connection  with  white  lead  does  not 
present  the  same  inconvenience  as  with  zinc  white. 

"To  the  afore-named  oxides,  we  should  add  the 
protoxides  of  the  metals  of  the  third  class  (Thenard's 
chemistry),  that  is  to  say,  those  of  iron,  cobalt,  and 
tin.  However,  as  the  greater  number  of  these  pro- 
toxides are  either  difficult  to  prepare,  or  rapidly  al- 
tered in  the  air,  they  cannot  be  kept  and  employed  in 
practical  operations.  We  have  therefore  searched 
out  as  to  whether  these  oxides,  combined  with  cer- 
tain bodies,  could  not  be  manufactured  in  an  economi- 
cal manner,  and  could  not  preserve  their  drying 
action  upon  oils,  from  the  time  that  they  are  prepared, 
to  that  when  they  are  employed. 

"  Moreover,  it  is  acknowledged,  that  dryers  in  the 
dry  state  are  preferable  in  many  respects  to  drying 
oils.  But  the  difficulty  lies  in  their  proper  prepara- 
tion. 

"  The  preceding  considerations  caused  me  to  search 


582 


MANUFACTURE  OF  COLORS. 


for  a  process  for  producing  the  drying  of  the  oil  em- 
ployed with  zinc  white,  without  litharge  or  any  oxide 
of  lead.  A  similar  result  has  been  arrived  at  by  other 
persons  with  more  or  less  success. 

"I  have  therefore  availed  myself  of  the  indications 
furnished  by  various  authors  upon  the  choice  of  cer- 
tain materials,  while,  on  the  other  hand,  I  have  made 
original  researches  and  experiments  based  upon  a 
theory  which  it  is  not  necessary  to  explain  in  this 
place. 

"  However,  I  should  say  that  one  of  the  principal 
bases  of  my  process  is  founded  upon  the  combination 
of  the  protoxides  of  the  metals  of  the  third  class 
(Thenard's-  chemistry),  that  is,  those  of  iron,  tin, 
nickel,  manganese,  and  cobalt,  with  benzoic,  succinic, 
urobenzoic,  and  boric  acids,  which,  at  the  same  time 
that  they  preserve  these  oxides  from  the  oxygen  of 
the  air,  do  not  prevent  them  from  acting  upon  the 
oils  as  a  ferment,  which  causes  the  absorption  of  the 
oxygen  of  the  air  by  these  oils,  and  their  resinifica- 
tion  or  drying.  Any  acid,  combined  with  these  pro- 
toxides, with  sufficient  affinity  to  render  the  manu- 
facture of  such  dryers  easy  and  economical,  and  to 
preserve  them,  is  comprised  in  my  processes.  At  the 
same  time,  the  affinity  of  the  acid  for  the  protoxide 
should  not  be  so  strong  as  to  prevent  the  latter  from 
acting  upon  the  oils.  Carbonic  acid  is  disengaged 
by  the  action  of  the  air  in  contact  with  the  oils  mixed 
with  these  dryers. 

"I  could  include  within  these  claims  the  above- 
mentioned  protoxides,  although  they  have  been  indi- 
cated before  me ;  but  it  is  impossible  to  employ  them 
in  the  manner  specified  by  the  authors,  especially  the 
pure  protoxide  of  manganese. 


DRYING  AND  ADHERENCE  OF  COLORS.  583 

"The  various  experiments  which  I  have  made  up 
to  this  date,  prove  that  the  preference  should  be  given 
to  the  urobenzoate  and  to  the  borate  of  cobalt;  but 
economical  considerations  favor  the  employment  of 
the  urobenzoate  and  the  borate  of  manganese. 

"  I  shall  now  explain  the  processes  of  preparation 
and  of  manufacture,  which  I  have  followed. 

1.  Benzoate  of  Cobalt,  and  Benzoate  of  3fanganese. 

"Benzoic  acid  is  dissolved  in  boiling  water,  and 
the  stirred  liquor  is  gradually  saturated  with  powdered 
carbonate  of  cobalt,  until  all  effervescence  ceases,  and 
blue  litmus  paper  does  not  turn  red  in  the  liquor. 

"  The  excess  of  carbonate  is  separated  by  filtration, 
the  liquor  is  evaporated  to  dryness,  and  the  heating 
is  continued  until  the  salt  has  lost  all  its  water,  and 
has  become  of  a  light  brown  color.  The  salt  thus 
prepared  is  an  amorphous,  hard,  and  brownish  mate- 
rial, which  may  be  powdered  like  rosin,  and  which 
may  be  kept  in  the  pulverulent  state,  in  any  climate, 
simply  folded  in  paper. 

"An  experiment  made  by  me  with  this  drying  salt 
has  proven  that,  in  the  proportion  of  3  kilogrammes 
to  1000  kilogrammes  of  linseed  oil,  mixed  with  about 
1200  kilogrammes  of  zinc  white,  a  piece  of  painting 
was  dried  in  from  eighteen  to  twenty  hours.  The 
temperature  was  relatively  cold  and  wet,  and  between 
12°  and  15°  C. 

"  The  benzoate  of  manganese  is  prepared  in  the  same 
manner,  by  substituting  the  carbonate  of  manganese 
for  that  of  cobalt.  The  manganese  dryer  presents 
nearly  the  same  physical  characteristics  as  the  cobalt 
salt.  Applied  under  the  same  conditions,  it  dries  a 
little  more  rapidly,  and  a  little  less  is  needed. 


584 


MANUFACTURE  OF  COLORS. 


"The  high  price  of  benzoic  acid  induced  me  to 
search  for  a  congenerate  of  this  acid,  which  would 
form  saline  combinations  having  the  same  properties, 
and  which  would  be  cheaper. 

"I  have,  therefore,  tried  the  urobenzoic  (hippuric) 
acid,  which  my  experiments  have  proven  as  effica- 
cious. The  iirobenzoates  of  cobalt  and  of  manganese 
are  obtained  in  the  same  manner  as  the  benzoates  of 
these  bases. 

"  The  materials  which  I  have  experimented  upon 
are  relatively  too  expensive  for  industrial  uses ;  but 
there  is  every  hope  that  it  will  be  possible  to  obtain 
the  benzoic  and  urobenzoic  acids  in  an  economical 
manner. 

2.  Borate  of  Cobalt, 

"A  soluble  salt  of  cobalt,  the  sulphate  for  instance, 
is  dissolved  in  cold  water,  and  this  solution  is  precipi- 
tated by  a  cold  one  of  borax  (biborate  of  soda).  The 
precipitate  of  borate  of  cobalt  is  collected  upon  cloth 
filters,  washed  with  cold  water,  and  dried  in  the  air. 

"  The  borate  of  manganese  is  prepared  in  the  same 
manner  by  substituting  for  the  cobalt  salt  a  soluble 
one  of  manganese,  the  chloride  for  instance,  which  is 
cheap. 

"These  borates  are  kept  and  used  in  the  same 
manner  as  the  preceding  dryers. 

3.  Employment  of  Besins, 

"  "With  the  same  view,  that  of  preparing  a  dryer  in 
the  dry  state,  free  from  any  foreign  substance  which 
might  impair  its  drying  properties  and  render  it  hy- 
grometric,  I  have  tried  the  employment  of  resins, 
which,  from  their  acidity,  play  a  part  analogous  to 
that  of  the  acids  already  mentioned. 


DRYING  AND  ADHERENCE  OF  COLORS.  585 


"  Thus,  by  applying  to  cobalt  and  manganese  the 
process  hereinafter  described,  I  have  obtained  a  real 
drying  salt,  containing  no  substance  not  in  harmony 
with  the  effect  to  be  produced,  and  which  may  be 
kept  in  the  pulverulent  state  as  the  afore-mentioned 
drying  salt. 

"An  alkaline  resinate  of  potassa  or  soda  is  dis- 
solved in  hot  water,  and  this  solution  is  precipitated 
by  a  suitable  proportion  of  the  pure  sulphates  or 
chlorides  of  cobalt  or  manganese.  The  precipitate 
thus  formed  is  a  resinate  of  cobalt  or  manganese, 
which  is  collected  upon  cloth  filters,  washed,  and  dried. 

"These  resinates  are  amorphous,  and  are  powdered 
and  kept  in  the  same  manner  as  the  other  dryers. 
They  possess  the  same  properties,  and  are  employed 
under  the  same  conditions  and  in  the  same  proportions. 

4.  Borate  of  Manganese, 

"In  continuing  my  investigations,  especially  on 
the  employment  of  the  borate  of  manganese,  I  re- 
marked that  the  protoxide  of  manganese  absorbed  the 
oxygen  of  the  air  with  great  rapidity,  passed  to  the 
intermediary  degree  of  oxidization,  and  at  the  same 
time  separated  from  the  acid  with  which  it  was  com- 
bined. I  found,  also,  that  if  more  than  2  or  3  parts 
of  this  manganese  salt  per  1000  parts  of  zinc  white 
were  added,  the  paint,  especially  the  white  grounds, 
would  acquire  a  prejudicial  coloration. 

"  In  order,  therefore,  to  remedy  this  inconvenience, 
which  may  often  take  place  from  cai*elessness  in  com- 
pounding the  proportions,  I  have  been  obliged  to  find 
a  method  for  neutralizing  the  troublesome  effects  of  an 
excess  of  dryer  in  the  paint. 

"  I  mix  in  advance  the  borate  of  manganese  with  a 


'  685 


MANUFACTURE  OF  COLORS. 


certain  proportion  of  oxide  of  zinc,  and,  in  this  di- 
Inted  state,  tlie  proportion  of  dryer  with  the  zinc 
white  paint  may  be  in  excess  with  less  danger.  I 
will  however  remark  that  this  arrangement  does  not 
entirely  do  away  with  the  necessity  of  making  the 
proper  mixtures,  but  that  it  allows  of  a  certain  amount 
of  carelessness  or  ignorance  in  the  compounding  of 
the  paints. 

"The  following  is  the  manner  of  mixing  the  dryer 
with  a  certain  proportion  of  zinc  white,  and  how  this 
mixture  is  to  be  added  to  the  white  pigment  and  oil, 
before  painting : — 

"  A  thick  aqueous  magma  of  30  grammes  of  borate 
of  manganese  is  thoroughly  mixed  with  1  kilogramme 
of  recently  prepared  oxide  of  zinc,  of  the  first 
quality,  and  made  into  a  thin  paste  with  water.  The 
mixture  is  drained  upon  a  cloth,  then  pressed  and 
dried  in  a  stove  room.  It  is  kept  in  a  pulverulent 
state,  in  barrels,  or  in  paper  sacks. 

"This  proportion  of  dryer,  added  to  20  kilo- 
grammes of  zinc  white,  will  be  sufficient  to  dry  the 
paint  rapidly ;  and  should  the  proportion  of  zinc 
white  be  reduced  one-fourth  or  one-fifth,  or  that  of 
the  dryer  increased  in  the  same  proportion,  the  color 
of  the  paint  will  not  be  altered. 

"  The  borate  of  manganese  as  a  drj^er  is  so  ener- 
getic that  it  is  proper  to  reduce  its  action  in  the  fol- 
lowing manner  : — 

"  One  kilogramme  of  borate  of  manganese  is  pow- 
dered and  mixed  with  25  kilogrammes  of  zinc  white, 
first  with  the  hands,  and  then  in  a  revolving  drum. 

"  In  decoration  and  artistic  painting,  dryers,  what- 
ever they  be,  are  employed  only  with  bitumens  and 
lakes,  for  glazing,  that  is  to  say,  for  transparent  coats. 


DRYING  AND  ADHERENCE  OF  COLORS.  587 


The  zumatic  dryer  cannot  conveniently  be  used  for 
such  purposes,  on  account  of  the  opacity  and  body  of 
the  zinc  white  entering  into  its  composition.  I  have 
therefore  replaced  the  oxide  of  zinc  by  a  substance 
which  answers  the  same  object  as  alumina  in  lakes, 
that  is,  a  material  without  opacity,  and  affecting  in 
no  way  the  color  and  the  transparency  of  the  paints 
with  which  the  dryer  is  mixed. 

The  substance  employed  for  such  an  admixture 
with  the  borate  of  manganese,  or  with  the  other  salts 
already  mentioned,  is  the  pure  carbonate  of  zinc, 
obtained  by  the  precipitation  of  a  soluble  zinc  salt 
by  an  excess  of  a  solution  of  crystallized  carbonate 
of  soda. 

"  The  carbonate  of  zinc  may  be  replaced  by  the 
sulphate  of  baryta,  clay,  the  carbonates  of  lime  or 
magnesia ;  in  fact,  by  any  substance  which  becomes 
translucent  in  oil.  But  it  is  preferable  to  employ  the 
carbonate  of  zinc,  which  adds  to  the  value  of  the 
new  article,  and  cannot  be  considered  as  an  adulte- 
ration. 

"  This  new  product  has  been  called  zumatic  lake. 
It  is  prepared  according  to  the  following  formula, 
which  contains  about  as  much  borate  of  manganese 
as  the  zumatic  dryer : — 

Carbonate  of  zinc   .       .       .       .90  parts  in  weight. 
Borate  of  manganese      .       .       .10  " 
Linseed  oil      .....    90  " 

"The  whole  is  most  thoroughly  ground,  and  kept 
in  bladders  or  in  tin  tubes.  The  latter  are  preferable. 

"  Since  the  borate  of  protoxide  of  manganese  causes 
also  the  rapid  drying  of  the  oils  employed  in  the  pre- 
paration of  inks  for  typography,  lithographic  and 
copperplate  printing,  Messrs.  Barruel  &  Jean  have 


588 


MANUFACTURE  OF  COLORS. 


recommended  the  use  of  borate  of  manganese  in  the 
manufacture  or  the  employment  of  printing  inks. 

"  The  use  of  the  borate  of  protoxide  of  manganese 
may  still  be  extended  to  the  preparation  or  the 
employment  of  fixed  oil  varnishes,  since  they  acquire 
a  great  tendency  to  dry  without  loss  of  brightness  or 
tenacity. 

"  Lastly,  the  borate  of  manganese  may  be  very  ad- 
vantageously employed  in  the  preparation  of  patent 
leather  and  oil  cloths." 

SECTION  y. 

SPREADING,  DRYING,  AND  ADHERING  PROPERTIES  OF  OIL  PAINTS. 

Mr.  Chevreul  published  in  the  Annales  de  Physique 
et  de  Chimie,  1857,  a  very  important  memoir  on  oil 
painting,  which  is  a  real  treatise  on  that  art.  We 
should  have  liked  to  have  entirely  reproduced  this 
work  of  the  illustrious  chemist,  but  it  is  too  extensive 
for  this  volume.  We  shall  therefore  confine  oui'selves 
to  a  resume  and  the  conclusions  of  the  author  as 
follows : — 

"  Painting  is  done  with  two  objects  in  view,  either 
to  change  the  natural  color  of  the  surfaces  of  various 
articles,  or  to  protect  those  articles  by  rendering  their 
surfaces  less  easily  altered  by  air,  rain,  dust,  etc. 

"  Three  conditions  must  be  fulfilled  : — 

^' First,  The  paint  must  possess  sufficient  fluidity 
to  spread  with  the  brush,  and  also  be  viscous  enough 
to  adhere  to  the  surfaces  without  running,  and  to 
leave  coats  of  equal  thickness,  when  the  surfaces  are 
inclined,  or  even  vertical. 

"  Second,  The  applied  paint  must  become  hard. 

"  Third,  After  it  has  become  hard,  it  must  adhere 


DRYING  AND  ADHERENCE  OF  COLORS. 


strongly  to  the  surface  upon  which  it  has  been  ap- 
plied. 

^'I  have  proved  that  the  hardening  of  white  lead 
or  zinc  white  paints,  is  due  to  the  absorption  of  the 
oxygen  of  the  atmospheric  air.  And  since  pure  oil 
hardens,  we  see  that  the  hardening  is  the  effect  of  a 
primary  cause,  which  is  independent  of  the  dryer, 
white  lead,  or  zinc  white. 

"  Besides,  my  experiments  demonstrate  that  white 
lead  and  oxide  of  zinc  manifest  a  drying  property  in 
many  cases,  and  that  this  property  exists  also  in  cer- 
tain substances  which  are  painted — lead,  for  instance. 

"  Therefore,  the  painter  desirous  to  know,  at  least 
approximately,  the  length  of  time  necessary  for  his 
painting  to  become  dry,  will  have  to  consider  all  the 
causes  which  produce  that  effect.  Consequently,  a 
dryer  will  not  be  considered  as  the  only  cause  of  the 
drying  phenomenon,  since  this  phenomenon  is  assisted 
by  several  substances,  having  also  the  property  of 
drying  under  certain  circumstances.  Moreover,  there 
is  this  remarkable  fact,  that  WiQ  resultante  or  sum  of 
the  activities  (drying  powers)  of  each  of  the  substances 
entering  into  the  composition  of  the  paint,  cannot  be 
reckoned  by  the  sum  of  the  activities  of  each  sub- 
stance. Thus,  pure  linseed  oil,  the  activity  (drying 
power)  of  which  is  represented  by  1.985,  and  oil 
treated  by  manganese  with  an  activity  pf  4.719,  will, 
when  mixed,  possess  an  activity  of  30.828. 

"  If  there  be  substances  increasing  the  drying  pro- 
perty of  pure  linseed  oil,  there  are  others  which  seem 
to  act  in  the  opposite  direction.    For  instance  : — 

"Linseed  oil,  with  one  coat  applied  upon  glass, 
was  dry  after  17  days. 

"The  same  oil,  mixed  with  oxide  of  antimony,  took 


590 


MANUFACTURE  OF  COLORS. 


26  days  to  dry.  In  this  case,  the  oxide  of  antimony 
was  an  anti-dryer, 

"Linseed  oil,  mixed  with  oxide  of  antimony,  and 
applied  upon  a  cloth  painted  with  white  lead,  was 
dry  after  14  days. 

"  The  same  oil,  mixed  with  the  arseniate  of  pro- 
toxide of  tin,  and  applied  upon  the  same  cloth,  was 
not  hard  after  60  days. 

"  Oak  wood  appears  to  possess  the  anti-drying  pro- 
perty to  a  high  degree,  since,  in  the  experiment  of 
December  22,  1849,  three  coats  of  oil  took  159  days 
to  dry. 

"In  the  experiment  of  May  10th,  1850,  a  first  coat 
of  linseed  oil  was  dry,  only  on  the  surface,  after  32 
days. 

"Poplar  seems  to  be  less  anti-drying  than  oak, 
and  Norway  fir,  less  than  poplar. 

"In  the  experiment  of  May  10th,  1850,  three  coats 
of  linseed  oil  took  to  dry  :  27  days  for  poplar  wood, 
and  23  days  for  Norway  fir. 

"  If  there  be  a  drying  activity,  and  a  contrary  one, 
in  certain  substances,  I  have  no  doubt  that  there  are 
also  circumstances,  under  which  linseed  oil  is  not  in- 
fluenced by  the  nature  of  the  surface  upon  which  it 
has  been  spread.  For  instance,  in  the  experiences  of 
May  10th,  1850,  one  coat  of  linseed  oil  was  given  upon 
surfaces  of  copper,  brass,  zinc,  iron,  porcelain,  and 
glass;  and  in  every  case  the  oil  was  dry  after  48 
hours. 

"  I  hasten  to  say  that  I  do  not  pretend  to  classify 
all  the  substances  in  contact  with  linseed  oil,  or  any 
other  drying  oil,  into  drying,  anti-drying,  and  neu- 
tral or  indifferent,  because  the  circumstances  under 
which  these  substances  are  placed  may  cause  varia- 


DRYING  AND  ADHERENCE  OF  COLORS.  591 


tions  in  their  properties.  I  believe  that  a  substance 
may  be  drying,  or  anti-drying,  under  different  circum- 
stances, whether  it  be  due  to  the  temperature,  or  to 
the  presence  or  absence  of  another  substance,  etc. 
For  instance,  metallic  lead  is  drying  towards  pure 
linseed  oil ;  whereas,  white  lead,  which  is  well  known 
as  possessing  drying  properties,  is  anti-drying  towards 
linseed  oil  applied  upon  metallic  lead. 

If  painters  desire  to  understand  their  operations 
well  they  must  consider  the  drying  of  their  painting 
in  the  same  manner  as  I  have  just  pointed  out.  By 
so  doing,  and  in  certain  determined  cases  differing 
one  from  the  others,  they  will  be  enabled  to  modify 
and  improve  their  ordinary  methods.  Linseed  oil  is 
naturally  dr^nng,  and  this  property  increases  almost 
always  by  its  admixture  with  white  lead,  and  in  cer- 
tain cases,  with  oxide  of  zinc.  If  the  mixture  be  not 
sufficiently  drying,  recourse  is  to  be  had  to  an  addi- 
tion of  oil  boiled  with  litharge  or  manganese.  At 
the  same  time  it  is  necessary  to  consider  the  nature  of 
the  surface  painted  over,  whether  it  be  a  first,  second, 
or  third  coat,  the  temperature  of  the  air,  the  light,  etc. 

"  From  our  present  point  of  view,  drying  oil  boiled 
with  litharge  or  manganese  loses  part  of  its  impor- 
tance, because  it  may  be  dispensed  with  for  the  second 
and  third  coats,  and  even  for  the  first  one  if  the  natu- 
ral drying  is  aided  by  the  temperature. 

"Moreover,  pigments  themselves  may  act  as  sub- 
stitutes for  it,  as  in  the  case  ot  light  colors,  which  are 
altered  by  yellows  or  browns,  if  the  painter  has  de- 
rived profit  from  some  of  the  observations  indicated 
in  this  memoir. 

"  Thus,  linseed  oil,  exposed  to  the  air  and  to  light, 
becomes  drying,  and  loses  its  color ;  it  may  therefore 


592 


MANUFACTURE  OF  COLORS. 


be  employed  with  white  lead  or  zinc  white,  without 
impairing  the  whiteness  of  either. 

Since  by  associating  oxide  of  zinc  with  carbonate 
of  zinc,  it  is  possible  to  dispense  with  a  dryer,  we 
have  a  new  way  of  avoiding  the  inconveniences  of 
colored  dryers.  At  the  same  time,  it  gives  a  hope 
that  new  combinations  of  colorless  substances  will 
be  found  presenting  greater  advantages  than  those 
just  noticed. 

"My  experiments  demonstrate  that  the  processes 
generally  followed  by  color  manufacturers,  for  render- 
ing oils  drying,  that  is,  by  heating  them  with  metallic 
oxides,  are  open  to  the  objections  of  waste  of  fuel  and 
coloration  of  the  product.    Indeed,  I  have  shown — 

"1.  That  oil  kept  at  the  temperature  of  70°  C,  for 
eight  hours,  has  its  drying  property  considerably  in- 
creased. 

"  2.  That,  if  peroxide  of  manganese  be  addeS  to 
the  oil  kept  at  this  temperature,  it  becomes  sufficiently 
drying  for  use. 

"  3.  That  a  very  drying  oil  will  be  obtained  by 
heating  linseed  oil,  for  three  hours  only,  with  15  per 
cent,  of  metallic  oxide,  and  at  the  temperature  gene- 
rally adopted  by  color  merchants. 

"  My  experiments  explain  perfectly  well  the  role 
of  linseed  oil,  or  more  generally  speaking,  of  drying 
oils,  in  painting.  Indeed,  when  oleic  acid  is  mixed 
with  metallic  oxides  which  may  solidify  it,  it  passes 
instantaneously  from  the  liquid  to  the  solid  state, 
and  there  is  no  uniformity  in  the  ensemble  of  the 
molecules  of  the  oleate.  The  effect  is  different  when 
a  drying  oil,  absorbing  oxygen,  passes  progressively 
to  the  solid  state.  The  slowness  with  which  the 
change  takes  place  allows  of  the  symmetrical  arrange- 


BRONZIN^G. 


593 


ment  of  the  oily  molecules,  which  would  appear  trans- 
parent if  there  were  not  opaque  molecules  between 
them.  But  if  the  latter  do  not  predominate,  the 
arrangement  is  such  that  the  painting  is  glittering, 
and  even  brilliant,  because  the  light  is  reflected  by 
the  dry  oil  as  by  a  looking-glass. 


CHAPTER  IV. 

BRONZING. 

Certain  articles  of  plaster  of  Paris,  wood,  paper, 
and  pasteboard,  are  given  a  bronze  color,  which 
varies  with  the  kind  of  bronzing  stuff  employed, 
and.  which  more  or  less  resembles  real  bronze. 

1.  A  very  brilliant  bronzing  is  done  with  the 
cuttings  of  gold-beater's  foil,  ground  under  a  muller 
with  honey.  The  object  to  be  bronzed  is  coated  with 
linseed  oil,  and  the  metallic  powder  is  applied  upon 
it  with  a  rag. 

2.  Mosaic  gold  {aurum  mussivum)  may  be  employed 
for  the  same  purpose,  after  having  been  finely  ground 
with  6  parts  of  calcined  bones.  A  small  quantity 
of  this  mixture  is  taken  upon  a  wet  cloth  and 
applied  upon  the  object.  The  bronze  coat  is  then 
rubbed  with  a  dry  rag,  and  afterwards  burnished. 

When  mosaic  gold  is  to  be  applied  upon  paper  it 
is  not  mixed  with  calcined  bones,  and  the  size  is  the 
white  of  egg  or  a  thin  alcohol  varnish.  The  bronze 
is  applied  with  a  brush,  and  is  afterwards  burnished. 

3.  When  a  clean  piece  of  iron  is  immersed  in  a  hot 
solution  of  sulphate  of  copper,  it  soon  becomes 

38 


594 


MANUFACTURE  OF  COLORS. 


covered  with  a  precipitate  of  metallic  copper,  which, 
after  being  washed,  is  ground  with  six  times  its 
weight  of  calcined  bones,  and  may  be  used  for 
bronzing  in  the  manner  before  explained. 

4.  Sometimes  it  is  desired  to  cover  articles  with  a 
gray  color,  resembling  that  of  iron,  and  which  is 
called  white  hronze.  An  agreeable  appearance  is 
imparted  hj  argentum  mussivum;  but  finely-powdered 
tin  is  also  used.  This  powder  is  prepared  by  pour- 
ing molten  tin  into  a  box,  the  sides  of  which  have 
been  well  rubbed  with  chalk,  and  shaking  the  metal 
very  rapidly  and  continuously  until  it  has  become  cold. 
This  powder,  passed  through  a  silk  sieve,  and  sized 
with  a  solution  of  glue,  is  applied  with  a  brush. 
The  coat  has  a  dead  lustre,  which  may  be  rendered 
bright  by  burnishing. 

The  argentum  mussivum  is  prepared  with  equal 
parts  of  bismuth,  tin,  and  mercury. 

When  plaster  of  Paris  is  to  be  bronzed  a  gray  color, 
it  is  rubbed  with  plumbago. 

5.  When  cleansed  and  scoured  cast-iron  is  dipped 
into  a  weak  solution  of  sulphate  of  copper,  it  becomes 
covered  with  a  film  of  metallic  copper,  which  is  quite 
adhesive.  In  this  case,  the  hue  of  the  copper  is 
reddish,  passing  to  a  brown  yellow. 

SECTION  1. 

REAL  BRONZE,  COLOR  WHICH  IT  ACQUIRES  IN  THE  AIR. 

Bronze,  exposed  to  the  air  for  a  greater  or  less 
length  of  time,  becomes  covered  with  a  very  thin  coat 
of  carbonate,  which  imparts  to  it  a  greenish  tinge,  called 
old  bronze  (patine).  "Various  processes  have  been 
proposed  to  produce  this  appearance  in  a  short  time; 


BRONZIXG. 


595 


but  however  close  the  resemblance  may  be,  a  prac- 
tised eye  will  discover  a  difference.  The  lovers  of 
antique  bronzes  should  not  complain  of  this  result, 
since  they  posess  a  means  of  distinguishing  really  old 
articles  from  their  imitations. 

A  color  resembling  more  or  less  that  of  old  bronze, 
is  given  to  bronze  ornaments  and  medals,  by  covering 
their  surfaces  with  various  mixtures. 

SECTION  II. 

VARIOUS  BRONZE  COMPOSITIONS  FOR  METALS. 

A  great  many  compositions  and  pickles  have  been 
proposed  for  producing  a  desired  patine.  Several  of 
these  compositions  have  constantly  given  good 
results ;  but  the  success  depends  a  great  deal  upon 
the  mode  of  operation,  and  different  operators,  using 
the  same  composition,  will  often  produce  patines  of 
different  hues.  The  following  are  several  of  these 
recipes : — 

The  metal,  turned  or  filed,  is  cleansed  with  nitric 
acid,  and  then  covered  with  the  mixture,  which  is 
uniformly  applied  by  means  of  a  soft  brush,  a  rag,  or 
a  pad. 

The  nature  of  the  alloy  itself  has  a  great  influence 
on  the  bronze  color  obtained.  Since,  therefore,  the 
alloys  of  articles  for  ornaments  vary  considerably, 
the  same  bronze  composition,  applied  in  the  same 
manner,  will  give  different  results. 

1.  I^itric  acid,  diluted  with  2  or  3  parts  of  water, 
is  spread  upon  the  article.  The  color  appears  gray 
at  first,  but  afterwards  it  passes  to  a  greenish  blue. 

2.  The  object  is  wet  several  times  with  a  liquor 
composed  of  1  part  of  sal-ammoniac,  3  of  carbonate 


596 


MANUFACTURE  OF  COLORS. 


of  potassa,  and  6  of  common  salt  dissolved  in  12 
parts  of  boiling  water,  to  which  are  afterwards  added 
8  parts  of  nitrate  of  copper.  The  coat  is  unequal 
and  raw  at  the  beginning,  but  it  soon  becomes  softer 
and  more  uniform. 

3.  A  handsome  blue-green  bronze  may  be  obtained 
with  concentrated  ammonia  alone  with  which  the 
article  is  many  times  rubbed. 

4.  The  basis  of  a  great  many  compositions  is  vine- 
gar with  sal-ammoniac.  Many  skilful  workmen  never 
use  anything  else  but  a  solution  of  60  grammes  of 
sal  ammoniac  in  1  litre  of  vinegar. 

5.  Another  pickle,  which  gives  very  good  results, 
is  a  solution  of  30  grammes  of  sal  ammoniac,  and  8 
grammes  of  sorrel  salt,  in  10  litres  of  vinegar. 

6.  A  skilful  chaser  of  Paris  uses  a  mixture  of  15 
grammes  of  sal  ammoniac,  15  of  common  salt,  30  of 
carbonate  of  ammonia,  and  1  litre  of  vinegar. 

7.  Another  good  composition  is :  15  grammes  of 
sal  ammoniac,  15  grammes  of  common  salt,  15  of 
aqua  ammonia,  and  1  litre  of  vinegar. 

A  brush,  dipped  into  this  mixture,  is  rubbed  upon 
the  cleansed  article  until  it  has  acquired  a  fine  bronze 
color.  The  piece  should  only  be  moistened,  and  any 
remaining  dampness  is  removed  with  another  brush. 

If,  after  two  or  three  days,  the  coat  appears  too 
pale,  the  operation  is  begun  anew.  The  work  may 
be  done  in  the  open  air,  which  causes  the  color  to 
appear  sooner.  The  metal  never  requires  to  be 
heated. 

Good  effects  are  also  obtained  with  the  two  follow- 
ing compositions : — 

8.  Sal  ammoniac  and  common  salt,  each,  8  grammes; 
aqua  ammonia,  16  grammes;  vinegar,  |  litre. 


BRONZING. 


597 


9.  Sorrel  salt,  2  grammes;  sal  ammoniac,  8 
grammes  ;  vinegar,  ^  litre. 

This  mixture  is  applied  with  a  slightly  moist  brush, 
the  application  being  continued  until  the  desired  tint 
is  obtained.  These  compositions  give  a  better  color- 
ation when  the  operation  is  conducted  in  a  clear  and 
aerated  place,  instead  of  a  dark  room. 

Medals  are  colored  in  a  somewhat  different  manner, 
and  the  pickles  also  greatly  vary. 

10.  A  thick  paste  is  made  in  vinegar,  of  an  inti- 
mate mixture  of  500  grammes  verdigris,  and  333 
grammes  of  sal  ammoniac.  A  volume  of  this  paste, 
about  equal  to  a  walnut,  is  boiled  and  stirred  in  a 
certain  quantity  of  vinegar  diluted  with  water. 
After  a  boil  of  fifteen  minutes  the  liquor  is  allowed 
to  settle,  and  is  then  decanted.  The  medals  are  boiled 
for  five  or  six  minutes  in  the  clear  liquor,  and  are 
afterwards  well  washed. 

The  same  liquor  cannot  be  used  more  than  five  or 
six  times,  and  a  small  quantity  of  vinegar  is  added 
at  each  operation. 

The  boiling  is  effected  in  copper  vessels,  and  the 
medals  are  separated  from  the  vessel  and  from  each 
other  by  means  of  small  pieces  of  wood.  The  medals 
should  be  immediately  wiped  off  after  the  coloring 
and  washing,  otherwise  their  hue  will  change.  When 
they  are  perfectly  dry,  a  bright  lustre  may  be  given 
to  them  by  another  stroke  of  the  press. 

It  often  happens  that  a  portion  of  the  medal  acquires 
a  bad  color  or  is  spotted. 

11.  The  operation  is  conducted  in  the  same  manner 
with  a  mixture  of  510  parts  of  verdigris,  and  250 
parts  of  sal  ammoniac,  ground  on  a  slab  with  vinegar. 
The  mixture  is  kept  in  well-closed  vessels.  When 


598 


MANUFACTURE  OF  COLORS. 


it  is  needed  for  use,  a  small  proportion  of  it,  as  in 
the  previous  recipe,  is  boiled  for  ten  or  twelve 
minutes  in  a  tumblerful  of  vinegar  diluted  with  2 
litres  of  water. 

The  alloys  holding  lead  and  tin  are  handsomely 
bronzed  with  a  mixture  of  100  parts  of  a  neutral  and 
pure  solution  of  nitrate  of  copper  marking  18°  Be., 
and  20  parts  of  sal  ammoniac.  The  articles  should 
be  barely  moistened  with  this  liquor. 

As  a  matter  of  curiosity,  we  here  give  the  Chinese 
j)rocess  for  bronzing : — 

The  copper  is  washed  with  vinegar  and  wood  ashes, 
until  it  is  perfectly  bright.  It  is  then  dried  in  the 
sun  and  smeared  with  the  following  composition  :  2 
parts  of  verdigris,  2  of  cinnabar,  5  of  sal  ammoniac,  2 
of  the  beak  and  the  liver  of  a  duck,  and  5  of  alum,  the 
whole  thoroughly  mixed  and  made  into  a  thin  paste 
with  water.  The  smeared  copper  article  is  then 
heated,  cooled,  and  wiped  off.  The  operation  is 
repeated  eight  or  ten  times.  The  copper  acquires  a 
handsome  appearance,  and  the  bronzing  is  so  durable 
that  it  loses  nothing  of  its  beauty  by  exposure  to  the 
rain  and  air. 

A  fine  bronze  may  be  obtained  with  a  mixture  of 
1  part  of  sal  ammoniac,  3  parts  of  cream  of  tartar,  and 
3  of  common  salt,  the  whole  being  dissolved  in  12 
parts  of  hot  water,  to  which  are  added  8  parts  of  a 
copper  solution. 

By  increasing  the  proportion  of  common  salt,  the 
coloration  is  lighter  and  tending  towards  yellow ;  by 
diminishing  or  suppressing  it  entirely,  the  coloration 
is  bluish.  The  action  is  more  rapid  if  the  mixture 
contains  more  sal  ammoniac. 

There  are  certain  articles  for  which  a  red  bronze  is 


BRONZIXG. 


599 


desirable,  and  which  are  smeared  with  oxide  of  iron. 
If  these  pieces  be  rubbed  nearly  dry  with  a  liquor 
holding  about  gV  of  sulphide  of  potassium,  and  then 
exposed  to  the  fire,  the  coloration  turns  to  a  greenish- 
brown. 

SECTION  III. 

RECIPE  FOR  THE  ORDINARY  BRONZE  OF  THE  FOUNDERS. 

Take- 
Strong  vinegar   1  litre. 

Sal  ammoniac   30  grammes. 

Alum         .   15  " 

Arsenious  acid  (white  arsenic)  .       .       .  8  " 

Mix  the  whole  together,  and  when  the  salts  are  dis- 
solved, the  liquor  is  ready  for  use.  A  good  bronze 
is  obtained  from  sal  ammoniac  alone,  in  vinegar,  and 
many  founders  employ  nothing  else.  Indeed,  with  a 
good  alloy,  success  is  almost  certain. 

After  the  casting,  the  metal  is  polished  with  a  fine 
cut  file,  or  upon  the  lathe,  or  with  sand  paper,  or  by 
a  dipping  in  nitric  acid.  It  is  absolutely  necessary, 
for  the  success  of  the  operation,  that  the  metal  should 
be  perfectly  clean,  and  especially  free  from  grease. 
Aqua  fortis  (nitric  acid)  is  the  best  cleansing  agent, 
and  it  should  be  employed  when  a  handsome  finish  is 
desired.  The  other  methods,  however,  are  sufficient 
for  ordinary  work. 

SECTION  lY. 

MODE  OP  APPLYING  THE  BRONZING  MIXTURES. 

The  bronze  mixture  is  applied  with  a  small  brush, 
and  the  articles  should  be  kept  constantly  moist 
during  the  operation,  in  order  not  to  become  green. 


600 


MANUFACTURE  OF  COLORS. 


When  the  desired  color  is  obtained,  which  generally 
requires  from  25  tg  30  minutes,  the  work  is  rapidly 
passed  through  clear  cold  water,  dried  in  tepid  saw- 
dust, and  then  varnished,  in  order  to  preserve  the 
coloration. 

It  happens  quite  often  that,  on  account  of  the 
quality  of  the  alloy,  the  bronze  composition  does  not 
produce  a  sufficiently  dark  coloration.  The  follow- 
ing is  the  best  manner  of  remedying  this  inconve- 
nience : — 

Take  about  8  grammes  of  the  best  lampblack,  stir 
it  with  about  one  tumblerful  of  rectified  alcohol,  and 
pass  the  liquor  through  a  cloth.  The  piece  upon 
which  the  bronze  composition  has  been  applied,  should 
be  heated  upon  a  metallic  plate  or  before  a  clear  fire, 
until  it  can  scarcely  be  held  in  the  hand.  Then,  with 
a  camel's-hair  brush,  thin  coats  of  the  lampblack 
liquor  are  spread  upon  it,  so  long  as  the  desired  tone 
is  not  yet  reached. 

When  the  coats  have  become  entirely  cold,  they 
are  polished  with  a  very  soft  brush,  or  with  a  rag 
dipped  in  very  limpid  green  oil.  The  whole  is  then 
varnished,  and  thus  is  obtained  the  finest  bronze  color 
which  can  be  imparted  to  an  alloy  of  zinc  and  copper. 
If  the  mixture  of  lampblack  be  not  too  black,  and  the 
varnish  of  too  light  a  yellow,  the  color  of  the  bronzed 
alloy  will  be  of  a  splendid  deep  green.  We  may  infer 
from  it,  that  it  is  possible  to  obtain  all  the  tones  of 
green  hronzes  by  using  more  or  less  of  the  lampblack 
mixture,  employing  a  varnish  more  or  less  yellow,  and 
giving  a  greater  or  less  thickness  to  the  coats  of 
black.  However,  the  article  will  keep  its  color  longer, 
if  the  coat  due  to  the  bronze  composition  be  made 
dark  enough  to  dispense  with  the  lampblack.  This 


BRONZING. 


601 


can  be  done,  but  more  time  is  required  than  when  the 
black  is  employed. 

SECTION  Y. 

MODE  OF  GIVING  THE  PROPER  BRONZE  COLORATION  WITHOUT 
LAMPBLACK. 

When  the  coat  of  bronze  color  is  dry,  if  the  tone 
does  not  appear  deep  enough,  the  piece  is  placed 
before  a  bright  fire,  or  exposed  to  the  rays  of  the  sun, 
and  its  position  is  now  and  then  changed;  while  at  the 
same  time,  a  draft  is  avoided.  The  piece  is  then  rubbed 
with  a  soft  brush,  and  a  very  handsome  bronze  is  thus 
obtained.  This  method  is  somewhat  tedious,  and,  in 
case  of  hurry,  lampblack  is  more  advantageous. 

SECTION  YI. 

BRONZING  OF  GUN  BARRELS. 

They  are  rubbed  rapidly  with  melted  butter  of 
antimony,  and  the  operation  is  repeated  several  times. 
The  barrels  should  be  moderately  heated. 

SECTION  YIL 

BRONZING  PLASTER  OP  PARIS. 

Articles  of  plaster  of  Paris  may  be  mistaken  for  old 
bronze  (provided  they  are  not  handled),  if  they  be 
impregnated  with  a  copper  soap  proposed  by  MM. 
d'Arcet  and  Thenard.  The  following  is  the  mode  of 
operation : — 

Pure  linseed  oil  is  converted  into  a  neutral  soap, 
by  means  of  caustic  soda.  A  concentrated  solution 
of  common  salt  is  then  added,  and  the  boiling  is  con- 
tinued until  the  liquor  becomes  very  dense,  in  order 


602 


MANUFACTURE  OF  COLORS. 


that  the  grains  of  soap  shall  come  to  the  surface. 
The  soap  granules  are  collected  upon  a  cloth,  drained 
and  pressed,  so  as  to  deprive  them,  as  far  as  practica- 
ble, of  the  adhering  lye.  The  soap  is  then  dissolved 
in  pure  water,  and  the  solution  filtered  through  a 
cloth.  Another  solution  is  made,  also  in  pure  water, 
of  80  parts  of  sulphate  of  copper,  and  20  parts  of  sul- 
phate of  iron,  which  is  filtered,  and  which  receives 
the  soap  water  until  the  decomposition  is  complete. 
A  small  quantity  of  a  solution  of  the  two  sulphates 
is  then  added,  the  whole  is  well  stirred  and  boiled, 
and,  in  this  manner,  the  metallic  soap  is  mixed  with 
an  excess  of  the  sulphates.  The  precipitate  is 
thoroughly  washed  with  boiling  water,  and  then  with 
cold  water.  It  is  collected  upon  a  cloth,  drained, 
and  dried  as  completely  as  possible. 

On  the  other  hand,  1  kilogramme  of  pure  linseed 
oil  is  boiled  with  250  grammes  of  finely  powdered 
litharge,  then  filtered  through  a  cloth,  and  allowed  to 
settle  in  a  hot  room. 

A  mixture  is  then  made  in  a  stonewai^e  pot,  placed 
upon  a  steam  or  water-bath,  of  300  grammes  of  boiled 
linseed  oil,  160  grammes  of  the  metallic  soap,  and 
100  grammes  of  pure  white  wax.  The  whole  is  kept 
heated  long  enough  to  remove  all  dampness.  The 
article  of  plaster  of  Paris  is  also  heated  at  from  80° 
to  90°  C,  in  a  stove,  and  is  covered  with  the  hot  mix- 
ture. When  the  plaster  has  become  too  cold  for  the 
mixture  to  penetrate,  it  is  again  heated  to  the  same 
temperature,  and  consecutive  coats  of  the  composition 
are  thus  applied  until  the  plaster  of  Paris  no  longer 
absorbs  it.  The  piece  is  again  heated  in  the  stove 
for  a  few  minutes,  in  order  to  absorb  the  composi- 
tion which  may  remain  on  its  surface.    The  natural 


BRONZING. 


603 


porosity  of  plaster  of  Paris  is  such,  that  the  mixture 
will  be  absorbed  without  impairing  the  sharpness  of 
the  finest  parts  of  the  east.  The  mixture  will  pene- 
trate more  or  less  deep,  according  as  the  operation  is 
more  or  less  often  repeated. 

When  the  piece  has  acquired  the  desired  color,  a 
lustre  is  given  by  rubbing  it  with  a  pad  of  cotton. 
In  order  more  exactly  to  imitate  the  real  old  bronze, 
the  raised  parts  are  touched  with  shell  gold  (ground 
gold  foil).  This  process  allows  of  a  thorough  imita- 
tion of  medals,  statuettes,  vases,  etc.  The  plaster, 
which  has  been  thus  prepared,  resists  dampness  per- 
fectly well,  and  becomes  v^n-y  durable. 


SECTION  YIII. 

GREEN  BRONZE. 


Take- 


Strong  vinegar   1  litre. 

Mineral  green   15  grammes. 

Umber       .       .       .       .       i       .       .  15  " 

Sal  ammoniac   15  " 

Gum  Arabic   15  " 

Avignon  berries   60  " 

Green  copperas   15 


And  about  85  grammes  of  green  oats,  if  they  can  be 
had,  but  they  are  not  absolutely  necessary.  Dissolve 
the  salts  and  the  gum  in  separate  portions  of  the 
vinegar,  then  mix  the  whole  in  a  stoneware  pot.  Add 
the  Avignon  berries  and  the  oats,  and  boil  upon  a 
gentle  fire.  After  cooling,  filter  through  a  flannel 
bag.    The  liquor  is  then  ready  for  use. 


APPENDIX. 


Mill  for  grinding  colors. 

This  machine,  invented  by  Mr.  Eawlinson,  is  very 
simple.  It  is  intended  especially  for  neutralizing  the 
dangerous  effects  of  the  dust  of  lead  pigments,  which 
is  produced  in  great  quantity  in  the  ordinary  process 
of  grinding  upon  a  slab. 

This  mill  is  represented  in  Fig.  62. 


Fig.  62. 


A  is  a  solid  cylinder,  45  centimetres  in  diameter, 
and  from  12  to  15  in  height.  It  is  generally  made  of 
black  marble,  which  is  harder  and  more  easily  polished 
than  other  stones. 

B  is  a  concave  muller,  of  the 'same  material  as  the 
cylinder,  which  it  covers  for  about  one-third  of  the 
circumference.  It  is  absolutely  necessary  that  the 
curvature  of  this  muller  corresponds  exactly  with 


MILL  rOR  GRINDINGr  COLOKS. 


605 


that  of  the  cylinder.  It  is  covered  with  a  wooden 
cap     held  by  hinges  i    to  the  frame  E. 

The  area  of  this  muller,  in  contact  with  the  cylinder, 
is  about  6  times  that  of  an  ordinary  muUer ;  therefore 
the  useful  effect  and  the  economy  of  labor  in  its  use 
are  as  many  times  greater. 

Moreover,  the  motion  of  the  machine  is  more  rapid 
than  that  of  the  ordinary  hand  muller,  and  there  is 
less  fatigue  for  the  operator. 

We  should  observe  that  the  machine  here  described 
is  of  the  smallest  pattern,  and  that  a  man  of  ordinary 
strength  may  easily  move  a  cylinder  from  60  to  65 
centimetres  in  diameter,  and  have  his  production 
increased  in  the  same  proportion. 

C  is  a  bent  piece  of  iron,  firmly  fixed  aty.  It  acts 
as  a  pressure  spring  upon  the  muller,  and  the  pressure 
is  regulated  by  a  screw  c. 

D  is  a  scraper,  movable  around  the  points  d 
and  inclined  upon  the  cylinder.  However,  it  is  put 
in  this  position  only  when  it  is  desired  to  clean  the 
stone,  which  is  then  revolved  in  a  direction  oi^posite 
to  that  followed  during  the  grinding  proper.  This 
scraper  is  arranged  like  a  saw  upon  four  pieces  of 
wood  K  K ;  its  blade  is  formed  of  a  steel  spring  for 
clocks. 

E.  Wooden  frame,  supporting  the  apparatus  and 
the  hand  crank. 

F.  Drawer  for  the  cleaning  knives,  those  knives 
used  by  curriers  being  the  best. 

G.  Sliding  board  upon  which  the  color  falls. 

H.  Metallic  dish  for  receiving  the  scrapings. 

'No  pigment  is  put  upon  this  mill,  unless  it  has 
previously  been  powdered  in  a  cloth-covered  mortar, 
or  in  a  mill  for  dry  gi-inding.    This  first  preparation 


606 


APPENDIX. 


is  not  new,  and  is  as  necessary  as  in  the  old  mode  of 
grinding. 

When  the  color  has  been  mixed  with  water  or  oil, 
it  is  carried  by  a  spatula  upon  the  cylinder  near  the 
muller.  More  play  may  be  given  by  loosening  the 
screw  c;  but  this  is  not  necessary,  because  paint  may 
be  added  by  successive  quantities,  until,  after  several 
revolutions,  the  cylinder  is  entirely  covered. 

When  it  is  desired  to  clean  the  muller,  the  screw 
c  is  loosened,  and  the  wooden  cap  is  thrown  back- 
wards around  the  hinges  i  i.  The  muller-stone  may 
then  be  removed. 

A  few  revolutions  of  the  cylinder,  with  the  clean- 
ing knives  pressed  against  it,  are  sufficient  to  clean 
it  thoroughly. 

It  is  impossible  to  state  in  advance  the  quantity 
of  color  which  should  be  put  upon  this  mill,  or  how 
long  it  should  stay  there,  since  the  only  rule  is  the 
desired  degree  of  comminution.  But  experience  has 
proven  that  as  much  work  is  done  with  this  appara- 
tus in  three  hours,  as  in  a  whole  day  with  the  ordi- 
nary flat  slab  and  muller,  and  that  the  waste  is  much 
less. 

The  author  adds  : — 

1.  That  a  fly-wheel,  fixed  at  the  other  end  of  the 
crank  axle,  will  render  the  motion  more  uniform. 

2.  When  the  pigment  is  very  hard,  it  is  advisable 
to  increase  the  pressure  of  the  muller,  and  to  diminish 
the  velocity  of  the  rotation  of  the  cylinder. 

3.  Too  great  a  velocity  is  prejudicial  to  the  bright- 
ness of  delicate  colors,  especially  when  the  stones 
become  hot. 

The  inventor  also  recommends  a  process  for  pre- 
paring the  bladders  for  oil  colors.    A  small  wooden 


MILL  FOR  DRY  mDIGO. 


607 


peg  is  inserted  in  the  neck  of  the  bladder,  and  a  string 
is  tied  upon  it.  By  removing  the  peg  and  pressing 
the  bladder,  the  color  runs  out  upon  the  pallet.  It 
will  be  still  better  to  tie  the  bladder  upon  a  quill,  with 
the  point  on  top,  because  by  cutting  it,  the  color  may 
be  squeezed  out.  The  drying  of  the  color  remaining 
in  the  bladder  will  be  prevented  by  plugging  the 
quill  with  a  small  wooden  pin.  This  method  is 
cleaner  and  more  economical  than  that  of  perforating 
the  bladders  with  a  knife  blade. 

Mill  for  dry  indigo. 

Fig.  63  represents  an  ordinary  mortar  L,  made  of 
marble  or  of  some  other  hard  stone,  in  which  revolves 
a  muller  M,  which  is  pear-shaped. 


Fig.  63.  Fig.  64. 


Its  axis  revolves  at  N",  upon  two  pieces  of  oak 
wood  fastened  to  the  wall  Q.  Pins  are  put  in  o  o, 
in  order  to  retain  the  axis  in  its  jDlace.    P  is  the 


608 


APPENDIX. 


crank  handle.  R  is  a  movable  weight,  which  is 
added  when  it  is  desired  to  increase  the  weight  of 
the  muller. 

Fig.  64  represents  the  muller  and  its  axis  removed 
from  the  mortar.  The  lower  curve  of  the  muller 
should  correspond  with  that  of  the  mortar.  S  is  a 
deep  groove  in  the  muller. 

A  certain  quantity  of  coarsely  broken  indigo  is 
put  into  the  mortar,  and  the  rotary  motion  of  the 
muller  causes  the  pieces  to  fall  into  the  groove,  and 
to  become  finely  ground.  The  operation  will  be 
rendered  more  easy,  if  the  lower  part  of  the  groove 
be  made  slightly  wider. 

By  covering  the  mortar  with  two  pieces  of  wood 
meeting  in  the  middle,  and  having  a  hole  for  the 
passage  of  the  axis,  no  dust  will  escape. 

In  manufactories  the  mill  is  turned  by  steam  power. 

The  weight  E.  is  sometimes  replaced  by  a  fly- 
wheel, which  renders  the  motion  more  uniform,  and 
which  should  not  be  more  than  60  to  65  centimetres 
in  diameter,  if  made  of  cast-iron.  If  this  fly-wheel 
acts  at  the  same  time  as  a  driving  pulley,  the  strap 
should  be  about  10  centimetres  wide. 

Improvements  in  the  mamtfacture  of  oils,  varnishes, 
and  colors,  hy  MM,  Bessemer  and  J.  8,  (7. 
Heywood, 

The  improvements  which  we  are  going  to  describe 
are  principally : — 

1.  A  mechanical  apparatus  for  extracting  oils  and 
oleaginous  substances  from  the  materials  in  which 
they  are  held. 

2.  A  peculiar  treatment  of  these  oils  and  oleagi- 
nous substances,  still  combined  with  the  materials 


OILS,  VARNISHES,  AND  COLORS. 


609 


which  produce  them,  by  pure  water  or  alkaline  solu- 
tion, and  by  hydraulic  pressure  in  closed  vessels. 

3.  A  mode  of  regulating  the  heat  applied  to  var- 
nish vessels,  by  means  of  a  metallic  or  air-bath ;  a 
method  of  exhausting  and  condensing  the  vapors  of 
resins  and  oils  used  in  the  manufacture  of  varnishes  ; 
and  lastly,  a  mode  of  boiling  oils  for  the  preparation 
of  colors. 

4.  A  process  for  giving  more  body  and  opacity  to 
colors  produced  by  the  combination  of  silica  with  an 
alkali,  alkaline  earths,  or  metallic  oxides,  and  making 
vitrified  colors  from  them. 

5.  An  apparatus  or  mill  for  grinding  these  colors. 

I.  In  regard  to  the  mechanical  apparatus  for  ex- 
tracting oils  and  oleaginous  substances  from  the 
materials  in  which  they  are  held  ;  we  use  the  oil  press 
represented  by  the  following  figures  : — 

Fig.  65  is  a  side  view  of  the  apparatus. 

Fig.  66  is  a  horizontal  projection  of  the  apparatus. 


Fig.  65. 


Fig.  67  is  a  longitudinal  section  passing  through 
the  axis. 
39 


610 


APPENDIX. 


Fig.  68  is,  on  a  larger  scale,  a  horizontal  section  of 
part  of  the  cylinder. 


Fig.  68. 


The  frame  a  a,  of  one  solid  casting,  is  basin  shaped 
at  aW,  in  order  to  receive  the  oily  substances  which 
run  into  it  during  the  pressing;  aW  are  the  pedestals 
and  journals,  in  which  the  crank  axle  d  revolves.  On 
the  opposite  side  the  pedestals  a^a^  and  their  caps 
e  e,  maintain  the  pressure  cylinder  ff^,  which  is  made 
of  ordnance  bronze,  thick  enough  to  resist  a  consider- 
able internal  pressure.  This  cylinder is  doubled 
inside  with  a  bronze  pipe  the  outside  of  which  is 
spirally  grooved  like  a  screw,  the  square  threads  of 
which  are  very  close.  Small  conical  holes  are 
bored  in  the  groove,  and  through  the  whole  thickness 
of  the  pipe  n.  At  the  internal  diameter  of  the 
pipe  is  greater,  and  is  filled  with  the  steel  ring  1 1, 
The  other  diameter  n^v^  is  smaller,  and  is  provided 
with  an  external  steel  ring  u  u,  A  cylindrical  sack 
V  V,  open  at  both  ends,  and  made  of  fustian,  hair  cloth, 
or  of  any  analogous  permeable  substance,  fits  the 


OILS,  VARNISHES,  AKD  COLORS.  611 

inside  of  the  pipe  and  contains  another  cylinder 
of  wire-cloth  or  of  finely  perforated  sheet  iron.  All 
these  inside  fittings  are  stretched  and  maintained 
firmly  by  the  steel  rings  t  u.  The  cylinder  n  is  then 
introduced  into  f  f^^  as  far  as  the  recess  g  and  the 
tubular  piece  h  h  is  brought  in  contact  with  the  ring 
u.  The  screwed  plug  acting  also  as  a  stuffing 
box,  maintains  the  whole  tight. 

The  extremity  f^f^  of  the  cylinder  is  of  a  smaller 
diameter,  and  contains  the  ring  jj,  the  diameter  of 
which  regulates  the  pressure  supported  by  the  mate- 
rials operated  upon.  A  solid  piston  Jc  fits  the  inside 
of  n,  and  receives  its  to  and  fro  motion  from  the  con- 
necting rod  Z.  The  parallel  motion  is  kept  up  by 
the  small  wheels  m  m,  rolling  upon  the  guides  a*,  of 
the  bed  frame,  x  is  a  hopper,  bolted  upon  the  collar 
y^of  the  pressure  cylinder,  and  which  delivers  its 
contents  when  the  piston  7c  has  left  the  opening  free. 

are  holes  perforated  in  the  pressure  cylinder,  and 
communicating  with  those  of  the  doubling  pipe  n. 
The  oil  escapes  through  them,  f^f^  are  rings  main- 
taining the  cylinder  firmly  pressed  against  the  pedes- 
tals a^. 

"When  steam  power  is  directly  employed  for  giving 
motion  to  the  piston  of  the  press,  the  connecting  crank 
placed  at  should  be  fixed  at  such  an  angle  that, 
when  the  piston  7c  is  at  the  end  of  its  course,  the  pis- 
ton of  the  steam  engine  is  only  halfway  up,  that  is, 
when  the  power  of  the  steam  admitted  is  the  greatest. 
In  this  manner,  when  the  steam  engine  passes  by  its 
dead  points,  the  piston  7c  is  half  way  in  its  return 
motion.  When  another  motive  power  is  applied  for 
turning  the  crank  d  it  becomes  necessary  to  put  a 
fly-wheel  upon  the  axle  d\ 


612 


APPENDIX. 


When  this  apparatus  is  employed  for  the  extrac- 
tion of  linseed  oil,  the  seeds  are  ground  and  heated 
in  the  ordinary  manner,  and  then  introduced  into  the 
hopper.  Each  time  that  the  piston  h  goes  back,  the 
opening  under  the  hopper  is  left  free,  and  a  certain 
quantity  of  seeds  fall  into  the  tube  n.  "When  the 
piston  returns,  it  pushes  these  seeds  towards  the 
narrow  part  of  the  cylinder,  and,  as  the  friction 
resulting  from  the  narrow  passage  through  the 
ring  j  is  great,  the  pressure  upon  the  seeds  is  also 
considerable. 

This  ring  j  is  movable,  and  may  be  replaced  by 
others  having  a  greater  or  less  diameter,  as  it  is 
desired.  The  doubling  pipe  n  may  also  be  entirely 
removed  for  the  necessary  repair  of  worn-out  parts. 

The  action  of  the  piston  h  resembles  that  of  the 
piston  of  a  hydraulic  press  ;  the  seeds  are  pumped  in  on 
one  side,  and  pressed  out  on  the  other.  All  that  por- 
tion of  the  cylinder  where  the  seeds  are  held  is  lined 
with  hair-cloth  or  any  other  permeable  and  resisting 
substance.  Eents  and  other  damages  are  not  fre- 
quent, since  the  cloth  is  protected  on  the  outside  by 
the  tube  ti,  and  on  the  inside  by  a  metallic  cloth,  or 
a  piece  of  perforated  sheet-iron. 

The  pressed  oil  passes  through  the  above  linings, 
then  through  the  holes  of  the  inside  tube  and  of  the 
cylinder,  and  lastly  falls  into  the  basin  a\  It  may  be 
removed  by  the  pipe  y. 

Although  this  description  is  that  of  a  single  pres- 
sure cylinder,  it  is  evident  that  several  of  them  may 
be  fixed  upon  a  common  frame,  and  their  pistons  be 
set  in  motion  by  the  same  power.  In  this  case,  the 
cranks  w^ill  be  set  at  such  an  angle  that  the  resistance 
will  be  nearly  uniform.  We  prefer  a  cylindrical  form 


OILS,  VARNISHES,  AND  COLORS.  613 


for  the  piston  and  the  cylinder;  but  any  polygonal 
shape  will  do  just  as  well. 

In  the  foregoing  description  of  the  oil-press,  we 
have  not  indicated  any  mode  of  heating  the  oily  sub- 
stances ;  but,  as  it  is  sometimes  necessary  to  raise 
their  temperature,  we  will  give  the  manner  of 
doing  it. 

A  greater  length  and  a  greater  diameter  are  given 
to  the  pressure  cylinder,  and  the  basin  a'  is  divided 
into  two  distinct  compartments.  A  strong  wrought- 
iron  pipe  is  introduced  into  the  axis  of  the  cylinder 
through  the  open  end,  and  reaches  about  midway 
towards  the  hopper.  The  extremity  of  the  pipe  inside 
of  the  cylinder  terminates  in  a  point,  while  the  other 
rests  against  a  framework,  which  gives  it  the  power 
of  resisting  the  pressure  tending  to  push  it  out  of  the 
apparatus.  No  steam  escapes  into  the  cylinder,  since 
the  pipe  is  not  perforated. 

The  ground  seeds  which  fall  from  the  hopper  are 
pressed  first  in  that  portion  of  the  apparatus  where 
the  pipe  does  not  reach,  and  give  out  a  certain  pro- 
portion of  cold  oil,  which  is  collected  in  the  first  com- 
partment of  a' ,  Being  pressed  further  on,  the  seeds 
are  obliged  to  pass  through  the  annular  space  between 
the  steam-heated  pipe  and  the  cylinder.  There  the 
oily  paste  absorbs  the  heat  rapidly,  and  abandons  a 
proportion  of  oil,  which  falls  into  the  second  com- 
partment of  a'.  We  see,  therefore,  that  the  two  ope- 
rations of  cold  and  hot  pressing  are  effected  simul- 
taneously. 

II.  Our  mode  of  extraction  of  oils  and  oleaofinous 
substances  still  contained  in  the  vegetable  or  animal 
materials,  by  a  treatment  with  pure  water  or  alkaline 
solutions,  and  with   hydraulic   pressure  in  closed 


614 


APPENDIX. 


vessels,  has  been  applied  with  the  apparatus  which 
we  shall  now  describe. 

Fig.  69  is  a  longitudinal  view,  and  Fig.  70  a  lon- 
gitudinal section  of  the  apparatus. 


Fig.  69. 


A  is  a  cast-iron  reservoir,  rounded  at  the  ends,  and 
open  on  top.  b  is  a  cylinder  with  hemispherical  ends, 
fastened  to  A,  and  able  to  resist  a  pressure  of  36 


OILS,  VAllNISHES,  ANT>  COLORS. 


615 


atmospheres.  This  cylinder  is  kept  in  a  vertical 
position  by  a  collar  c,  which  forms  a  half  circle,  and 
is  fastened  by  bolts  upon  a  similar  collar  cast  on  a. 
The  upper  part  of  the  vessel  b  forms  a  cup  b\  the 
flange  of  which  supports  a  bracing  iron  hook  d.  The 
neck,  connecting  the  cup  and  the  vessel  b,  is  lined 
with  a  doubled-up  leather  e,  maintained  by  the  ring 
G.  The  bottom  of  the  vessel  is  also  provided  with 
another  doubled-up  leather  h,  maintained  by  the  bolted 
ring  J.  A  stout  iron  rod  k  extends  from  the  bottom 
of  B  up  to  the  top  of  the  bracing  hook  d.  The  por- 
tions are  of  a  larger  diameter  and  fit  the  doubled- 
up  leathers.  The  upper  part  of  k  has  a  square  thread 
K^,  cut  upon  it,  which  passes  through  d\  and  is  seized 
by  the  nut  ]sr,  moved  by  the  handles  p  p.  In  this 
manner  the  rod  k  may  be  raised  or  lowered. 

R  is  a  tube,  through  which  water  may  be  injected 
into  the  vessel  b,  by  means  of  a  pressure  pump,  similar 
to  those  employed  for  hydraulic  presses,  s  is  a  stop- 
cock used  for  letting  out  a  part  of  the  contents  of  the 
vessel,  or  removing  the  pressure  when  it  is  necessary 
to  do  so.  The  areas  of  the  stoppers  and  being 
equal,  the  pressure  exerted  inside  of  the  vessel  has  no 
tendency  to  push  the  rod  either  up  or  down,  and  the 
doubled-up  leathers  make  a  tight  joint. 

After  a  certain  portion  of  oil  or  oleaginous  sub- 
stances has  been  extracted  from  the  vegetable  or  ani- 
mal materials,  the  remaining  portions  are  more  diffi- 
cult to  obtain,  and  are  treated  in  the  following  manner. 
The  materials  are  removed  from  the  press,  and  then 
mixed  with  a  certain  proportion  of  hot  water,  or  of  a 
slightly  alkaline  lye,  in  order  to  make  a  semi-fluid 
paste,  which  is  introduced  into  the  above  described 
apparatus.    By  turning  the  handles  p  p,  the  stopper 


616 


APPENDIX. 


is  raised  above  the  opening  of  the  cnp,  whereas 
the  lower  one  k^,  which  is  much  longer,  keeps  the 
bottom  aperture  closed.  The  semi-fluid  materials  are 
then  introduced  into  the  cup  b\  which  delivers  them 
into  the  vessel  b.  The  rod  k  is  lowered,  so  as  to 
close  the  two  apertures,  and  the  hydraulic  pump  being 
set  in  motion,  the  materials  are  soon  submitted  to  the 
required  pressure. 

The  whole  is  allowed  to  stand  for  a  few  minutes, 
in  order  to  effect  the  reaction ;  then  the  stopcock  s 
is  opened,  and  a  portion  of  the  substances  fall  into 
the  reservoir  below.  By  moving  the  handles  p  p, 
the  stopper  is  raised  high  enough  for  the  remainder 
of  the  substances  to  flow  out.  The  rod  k  is  lowered 
again,  and  a  new  charge  is  put  into  b. 

The  pressure  exerted  upon  the  mixture  of  oleagi- 
nous substances  and  water  forces  the  inclosed  oil  to 
make  with  water  a  liquor  of  a  milky  appearance,  from 
which  the  oil  may  be  separated,  either  by  settling  in 
large  tanks,  or  by  evaporating  the  water. 

When  the  oils  are  intended  for  the  manufacture  of 
soap,  or  for  certain  other  uses,  the  mixture  needs  not 
to  be  separated.  When  seed  oil  is  thus  obtained,  the 
mucilaginous  substances  favor  the  combination  of  the 
two  liquids. 

As  soon  as  the  materials  have  been  removed  from 
the  reservoir  A,  they  are  drained  upon  sieves,  and  the 
solid  portions  are  again  pressed  for  extracting  the 
fluid  portions.  In  certain  cases,  it  is  advantageous 
to  boil  the  milky  liquor,  in  order  to  coagulate  the 
albuminous  substances,  and  facilitate  the  purification 
of  the  oil. 

III.  The  following  is  the  process  which  we  use 
for  regulating  the  heat  applied  to  varnish  vessels  by 


OILS,  VARNISHES,  AND  COLOKS. 


617 


means  of  metallic  or  hot  air  baths ;  and  our  method 
for  exhausting  and  condensing  the  vapo;s  disengaged 
from  resins  and  oils,  during  the  manufacture  of  var- 
nishes, or  from  boiling  oils  employed  for  the  prepara- 
tion of  colors. 

In  the  actual  method  of  preparing  varnishes,  the 
resins  and  gums  are  generally  liquefied  in  thin  copper 
pots,  placed  directly  over  the  fire.  The  temperature 
may  be  suddenly  raised  so  high  that  the  gums  are 
seriously  damaged,  and  often  catch  fire.  On  the 
other  hand,  equally  rapid  coolings  may  produce  other 
inconveniences.  Moreover,  at  the  high  temperature 
required  for  melting  copal,  amber,  resin  anime,  and 
other  analogous  substances,  their  more  volatile  por- 
tions form  abundant  fumes.  The  disengagement  of 
these  vapors  affects  the  men  powerfully,  and  some- 
times is  the  cause  of  dangerous  explosions.  On  the 
other  hand,  the  value  of  these  lost  vapors  is  consider- 
able, either  for  the  manufacture  of  varnish  or  for  other 
uses.  The  melting  pots  must  remain  open,  in  order 
to  watch  the  operations,  and  to  add  fresh  portions  of 
the  materials.  These  considerations  show  how  diffi- 
cult it  has  been  to  prevent  the  losses  by  volatilization, 
and  have  caused  us  to  search  for  the  process  which 
we  are  about  to  explain. 

Figs.  71  and  72  are  vertical  and  horizontal  sections 
of  the  apparatus  for  melting  the  resins  or  gum  resins. 

a  is  the  fireplace,  placed  below  the  floor  of  the 
work-room  as  usual ;  h  is  the  door  of  the  fireplace? 
and  c,  the  ash  pit.  Upon  this  fireplace  there  is  placed 
a  cast-iron  kettle  nearly  filled  with  an  alloy  of 
equal  parts  of  lead  and  tin,  because  the  melting  point 
of  lead  alone  is  too  high  for  our  purpose.  The  flame 
passes  through  the  flues  e  and  f  around  the  kettle : 


618 


APPENDIX. 


g  is  the  melting  pot,  made  of  thin  copper,  and  riveted 
to  the  collar  h.  The  pot  is  held  in  the  bath  by  three 
iron  hooks  ^,  ^,  %  which  pass  into  corresponding  places 
cut  in  the  collar  h ;  and  the  fastening  is  effected  by 
partly  turning  the  pot. 


Fig.  n.  Fig.  t2. 


On  top  of  the  pot  there  is  a  kind  of  hanging  lip  m, 
occupying  one-half  of  the  circumference,  and  stand- 
ing at  about  the  distance  of  12  millimetres  from  the 
inward  surface  of  the  pot.  The  opening  thus  left  on 
the  side  of  the  pot  is  covered  with  a  riveted  semi- 
circular conduit,  which  at  n  connects  with  the  pipe 
p  _p\  The  pipe  jp^  is  attached  to  a  cooling  worm, 
placed  in  a  tub  of  cold  water,  and  the  outlet  from  the 
worm  terminates  in  a  vertical  pipe,  the  lower  part  of 
which  is  closed  with  a  stopcock  and  receives  the  con- 
densed products,  while  the  upper  part  is  connected 
with  an  exhausting  apparatus,  which  is  constantly 
aspiring  the  vapors  into  the  cooling  worm,  and  de- 
livers into  the  air  the  uncondensable  products.  The 
following  is  the  manner  of  using  the  apparatus. 

When  the  fire  is  Hghted,  and  the  metallic  bath  is 


OILS,  VAKNTSHES,  AND  COLORS. 


619 


in  fusion,  a  thermometer  is  introduced  through  the 
opening  r,  and  the  temperature  noted.  As  soon  as 
the  required  temperature  is  reached,  the  melting  pot 
g  is  put  into  the  bath,  and  fastened  by  the  hooks  ^, 
care  being  taken  that  the  tubes  7i  and  p  should  cor- 
respond. A  charge  of  14  kilogrammes  of  amber,  for 
instance,  is  then- introduced  into  the  i^ot,  watched, 
and  stirred  in  the  ordinary  manner.  The  exhaust 
is  also  set  in  motion,  and  the  amher  oil,  or  volatile 
portion  of  the  amber,  follows  the  direction  of  the 
arrows,  being  drawn  by  suction  under  the  lip  m,  and 
from  thence  into  the  cooling  worm,  accompanied  by 
a  certain  proportion  of  air. 

There  is  no  great  difficulty  in  maintaining  a  suitable 
and  uniform  temperature  in  the  metallic  bath,  because, 
in  the  short  time  necessary  for  melting  a  charge,  the 
temperature  of  a  considerable  quantity  of  metal 
does  not  change  sensibly,  even  should  the  fire  be  much 
urged,  or  allowed  to  die  out.  Besides,  an  excess  of 
heat  may  be  reduced  immediately,  by  introducing  a 
large  piece  of  cold  iron  through  the  opening  r,  and 
leaving  it  in  the  bath  for  one  or  two  minutes.  In 
general,  we  may  feel  confident  that  the  temperature 
will  remain  constant  during  one  operation,  unless  the 
fire  be  entirely  neglected. 

"When  the  resin  is  melted  and  mixed  with  oil,  it 
should  be  removed  from  the  metallic  bath  into  the 
boiling  pot.    The  contents  are  poured  from  the  side 

Thus,  in  this  manner  of  melting  resins,  the  heat  has 
been  easily  regulated  without  escaping  fumes,  and 
with  a  condensation  of  volatile  products,  which  may 
be  utilized  advantageously  by  the  varnish  maker. 


620 


APPENDIX. 


Fig.  73  is  a  vertical  section  of  the  pot  for  boiling 
oils,  gums,  and  resins  in  the  manufacture  of  varnishes. 

The  same  pot  may  also  be  em- 
Fig.  73.  j)loyed  for  boiling  the  oils  em- 


ployed in  the  preparation  of 
paints. 

A,  copper  pot  of  the  ordinary 
shape ;  b,  flat  cast-iron  pan, 
which  is  made  very  thick,  in  or- 
der to  stand  and  retain  the  heat, 


and  thus  to  counterbalance  rapid 
changes  in  the  temperature  of  the  fire.  This  pan  is 
kept  over  the  fireplace  c,  by  means  of  the  flange  b'  b', 
which  rests  upon  the  brickwork  d.  The  copper  pot 
is  held  upon  the  air  bath,  by  means  of  the  riveted 
flanged  ring  a'.  The  cover  of  the  pot  is  an  annular 
inverted  gutter  e,  the  curvature  e'^  of  which  has  its 
edge  quite  close  to  the  sides  of  the  pot,  without,  how- 
ever, touching  them,  and  is  connected  by  means  of  the 
tube  H  with  a  cooling  worm  and  an  exhaust.  The 
mode  of  operation  is  as  follows: — 

The  heat  of  the  fireplace  o  is  transmitted  to  the 
pan  B,  and  the  air  contained  therein  communicates 
its  temperature  to  the  boiling  pot,  which,  therefore, 
is  not  so  much  exposed  to  irregularities  of  temper- 
ature as  if  it  were,  as  usual,  placed  directly  over  the 
fire.  The  suction  exerted  in  the  pipe  h  and  the  annu- 
lar space  G,  carries  away  the  vapors  emitted  by  the 
boiling  oils  or  varnishes,  and  forces  them  to  pass 
through  the  cooling  worm,  where  the  condensable 
portions  are  collected.  At  the  same  time,  the  large 
aperture  left  in  the  annular  cover  permits  of  the 
watching  of  the  operation,  and  of  the  stirring  of  the 
substances  with  the  spatula  i. 


OILS,  VARNISHES,  AND  COLORS. 


621 


As  this  shape  of  the  air  bath  requires  the  lifting 
upwards  of  the  pot  before  it  is  removed  from  the  fire, 
it  may  be  more  handy  to  give  to  this  air-bath  the 
shape  indicated  by  the  Figs.  74  and  75.    j  is  a  thick 


piece  of  cast  iron  with  a  ring  and  six  radial  ribs  k  k 
projecting  above.  The  spaces  Q  form  the  air-bath, 
L  is  the  fireplace ;  m,  the  brickwork  of  the  furnace, 
and  N,  the  bottom  of  the  copper  pan,  which  is  level 
with  the  top  of  the  furnace.  In  this  manner  the  pot 
may  be  made  to  slide  horizontally  from  the  hot  cast- 
iron  without  lifting  it. 

It  is  evident  that  a  metallic  bath  could  be  employed 
for  heating  the  oil  pot,  or  an  air-bath  for  dissolving 
the  resins,  but  we  believe  that  the  described  dispo- 
sitions are  sufficient. 

IV.  Our  processes  for  giving  more  body  or  opacity 
to  the  colors  produced  by  the  combination  of  silica 
with  alkalies,  alkaline  earths,  and  metallic  oxides,  and 
therefore  making  vitrified  pigments,  will  be  easily 
understood  by  the  following  description  : — 

In  several  arts,  in  painting  on  porcelain  and  glass, 
for  instance,  the  colors  employed  are  formed  of  the 
materials  we  have  indicated.  In  certain  cases,  it  is 
not  absolutely  necessary  that  the  colors  should  be 
opaque,  and  in  glass  painting,  on  the  contrary,  trans- 
parency in  the  colors  is  a  desideratum.  The  colors 
formed  by  the  combination  of  silica  with  alkalies. 


Fig.  U. 


622 


APPENDIX. 


alkaline  earths,  and  metallic  oxides,  are  remarkable 
for  their  resistance  to  the  action  of  air  and  dampness  ; 
therefore,  it  is  desirable  that  they  should  be  employed 
in  ordinary  painting,  but  it  is  also  absolutely  necessary 
that  they  should  possess  sufficient  body  and  opacity 
to  cover  well  the  materials  upon  which  they  are 
applied. 

It  is  known  that  several  kinds  of  glass,  especially 
those  which  contain  a  great  proportion  of  lime,  will 
have  their  molecular  arrangement  completely  changed 
by  a  long  exposure  to  a  not  very  intense  red  heat. 
From  an  ordinary  transparent  glass,  they  will  become 
a  semiopaque  material,  known  under  the  names  of 
devitrijied  glass  or  Hemimur^s  porcelain.  Basing  our- 
selves upon  this  fact,  we  propose  the  following  mode 
of  operation: — 

We  introduce  into  an  ordinary  glass  pot  a  mixture 
of  250  kilogrammes  of  white  sand,  100  kilogrammes 
of  dry  sulphate  of  soda,  85  kilogrammes  of  phosphate 
of  lime,  and  4  kilogrammes  of  charcoal,  the  latter 
being  added  for  decomposing  and  removing  the  acid 
of  the  sulphate  of  soda.  We  pour  the  melted  mix- 
ture, by  means  of  an  iron  ladle,  into  cold  water,  and 
the  suddenly  cooled  glass  is  reduced  to  small  frag- 
ments, which  are  immediately  heated  for  three  or 
four  days  at  from  370°  to  480°  C,  in  ordinary  gas 
retorts.  The  hot  fragments  are  then  again  raked  into 
cold  water.  They  become  still  more  disintegrated, 
and  are  so  brittle  that  they  are  easily  powdered 
under  ordinary  vertical  running  stones. 

The  devitrification  operated  in  the  retorts,  at  a  low 
and  protracted  heat,  still  increases  the  opacity  due  to 
the  phosphate  of  lime.    In  certain  cases,  when  an 


OILS,  VARNISHES,  AND  COLORS.  623 


extreme  degree  of  opacity  is  desired,  a  suitable  pro- 
portion of  oxide  of  tin  is  added. 

The  previously  indicated  mixture  gives  a  white 
opaque  glass  which  may  be  used  as  a  basis  for  all  the 
desired  colors. 

It  is  well  known  that  metallic  oxides  are  generally 
employed  for  coloring  glass;  these  oxides  are,  there- 
fore, combined  with  the  above  materials  before  their 
fusion  in  the  glass  pots,  and  in  proportions  to  suit  the 
desired  hues  or  tones  of  color.  We  shall  not  here 
examine  these  proportions,  since  our  present  object 
is  to  give  sufficient  body  and  opacity  to  vitreous 
compounds,  in  order  to  use  them  with  water  or  oils 
as  ordinary  paints. 

In  the  proportions  indicated  for  the  formation  of 
the  vitreous  basis,  it  is  possible,  if  so  desired,  to  ef- 
fect certain  changes;  for  instance,  potassa  may  be 
substituted  for  the  soda,  as  many  glass  manufacturers 
do.  "We  have  simply  given  the  recipe  which  has  ap- 
peared to  us  the  most  economical,  and  have  indicated 
the  sulphate  of  soda,  which  is  very  cheap  in  com- 
parison with  the  carbonates  of  soda  and  potassa. 

In  order  to  bring  the  devitrified  colors  to  the  proper 
degree  of  comminution,  they  are  first  powdered  under 
a  vertical  running  stone,  and  then  ground  with  oil 
or  water  in  a  color  mill.  This  grinding  should  be 
done  with  the  greatest  care,  and,  in  order  to  arrive  at 
this  result,  we  propose  the  apparatus  or  mill  we  are 
about  to  describe. 

V.  The  ordinary  mill  for  grinding  colors  is  com- 
posed of  a  pair  of  horizontal  stones,  the  lower  one  of 
which  is  stationary,  while  the  upper  one  revolves  on 
its  axis.  The  color  is  furnished  from  a  hopper,  which 
delivers  it  into  the  central  hole  of  the  running  stone; 


624 


APPENDIX. 


and  when  this  color  has  passed  between  the  stones,  it 
is  received  into  a  gutter,  fixed  to  the  bed  stone. 
Each  portion  of  the  running  stone  traverses  a  space 
proportional  to  its  distance  from  the  centre  ;  therefore 
at  each  revolution,  the  points  near  the  centre  travel 
less  than  those  near  the  circumference.  It  follows 
that  the  stones  must  wear  unequally,  and  that  their 
action  must  become  very  imperfect,  since  the  central 
portions,  being  but  slightly  worn  out,  prevent  a  suffi- 
cient contact  of  the  stones  near  their  edges.  More- 
over, the  simple  movement  of  rotation  of  the  upper 
stone  upon  the  lower  one  produces  a  series  of  con- 
centric ridges  and  hollows  which  prevent  the  intimate 
contact  and  the  action  of  the  stones  upon  the  particles 
of  material  to  be  ground.  The  wear  of  the  stones  is 
rapid,  and  at  the  same  time  the  grinding  is  very  im- 
perfect. In  oi'der  to  remedy  these  defects  we  have 
built  the  following  mill: — 

Fi^^.  76. 


Fig.  76  is  a  side  view  of  the  principal  pieces  of  the 
apparatus,  and  contains  also  a  central  section  of  one 
of  the  stones. 

Fig.  77  is  a  horizontal  view  of  the  mill. 

a  a  is  a  stout  wooden  frame,  which,  with  the  cover 
a'  a'  forms  a  kind  of  table,  upon  which  are  bolted  two 
rings  h  h,  with  flanges  c  c.    These  rings  are  cast  with 


OILS,  VARNISHES,  AND  COLORS.  625 


^  circular  gutter  for  receiving  the  ground  paint, 
which  is  drawn  out  by^^the  lips  ee,  ff  are  the  parts 
of  the  rings  which  support  the  bed  stones  g  made 
fast  with  a  cement  of  plaster  of  Paris.    At  each  end 

Fig.  11, 


of  the  frame  a  a  there  is  a  cranked  axle  A,  revolving 
in  the  step  ^,  and  on  top  in  the  collar y.  The  cranks 
of  the  two  axles  are  united  bj  the  connecting  rod  I, 
The  upper  extremities  of  the  axles  h  7i  are  fixed  to 
ordinary  cranks  mm,  the  pins  of  which  enter  conical 
sockets  n%  of  the  movable  frame  n  n,  formed  of 
iron  bars  inclosing  two  rings  n'  n'.  This  frame  acts 
also  like  a  connecting  rod.  The  cranks  Jc  connected 
by  I,  are  at  right  angles  with  the  cranks  mm,  so  as 
to  facilitate  the  passage  of  the  dead  points.  The 
heavy  pulley  o  receives  the  motion,  transmits  it  to  the 
whole  apparatus  by  means  of  the  connecting  rod  Z, 
and  of  the  rigid  frame  nn,  and  q  acts  as  a  fly-wheel. 

The  upper  stones  rr,  resembling  mullers,  are  pro- 
vided with  hoppers  s  s,  and  their  lower  surfaces  are 
slightly  bevelled  near  the  centre  to  facilitate  the  intro- 
duction of  the  materials  to  be  ground.  These  stones 
r  r  are  placed  in  the  rings  n!  7i\  where  they  have  suffi- 
cient play,  and  press  with  all  their  weight  upon  the 
bed  stones  g  g.  When  the  semifluid  materials  are 
poured  into  the  hoppers,  and  when  the  apparatus  is 
40 


626 


APPENDIX. 


set  in  motion,  these  stones  r  r  are  carried  by  the  frame 
nn^  and  travel  circles  equal  in  diameter  to  that  de- 
scribed by  the  cranks  m  m,  besides  their  movement 
of  rotation  npon  their  own  axis.  It  results  fi'om  this 
compound  motion,  that  all  the  points  of  their  surfaces 
travel  through  equal  spaces,  and  that  the  wear  is 
equal  in  all  their  parts.  In  order  to  cause  a  constant 
change  in  the  surfaces  of  contact,  a  play  of  1  centi- 
metre is  left  between  the  running  stones  and  the  en- 
closing rings  n'  n\  This  motion  is  the  same  as  that 
used  in  certain  mills  for  polishing  plate  glass.  These 
stones,  after  being  used  for  a  certain  length  of  time, 
become  perfectly  level,  and  therefore  more  effective, 
since  no  portion  of  the  color  can  escape  without 
having  been  ground  between  perfectly  fitting  surfaces. 
It  is  evident  that  the  degree  of  comminution  of  the 
particles  depends  upon  their  more  or  less  intimate  and 
protracted  contact  with  the  grinding  surfaces. 

Description  of  an  English  mill  for  grinding  colors. 

Fig.  78  is  a  view  of  the  mill  on  the  side  of  the 
crank  handle;  Fig.  79  is  a  front  view  of  the  same, 
and  Fig.  80  a  horizontal  view  from  above. 

The  same  letters  designate  the  same  parts  in  the 
three  figures. 

The  frame  A  is  of  wood,  strengthened  by  two  iron 
bars  B  B.  The  bed  stone  c  c  is  of  cast  iron,  and  its 
upper  face  has  radial  grooves  like  an  ordinary  mill- 
stone. It  is  fixed  upon  the  iron  bars  bb,  and  is  in- 
closed in  a  large  iron  ring  d  which  prevents  the  color 
from  running  out  except  through  the  opening  e. 
When  the  paint  is  sufficiently  ground  it  is  received 
in  the  vessel  x  placed  underneath. 

The  running  stone  r  is  also  of  cast  iron,  and  the 


ENGLISH  MILL  FOR  GRINDmG  COLORS.  627 

dotted  lines  indicate  its  shape.  The  central  hole  g  a 
and  the  circumference  have  a  raised  edge,  high 
enough  to  prevent  the  color,  inside  and  outside,  from 
getting  over  them. 


Fig.  78. 


A  vertical  shaft  h  supports  the  running  stone  f 
and  gives  it  its  motion.  The  horizontal  bevel  wheel 
K  is  of  cast  iron,  with  twenty-seven  wooden  cogs, 
and  is  fixed  to  the  top  of  the  shaft  h.  Another  ver- 
tical bevel  wheel  l,  with  twenty-seven  cogs,  is  placed 
upon  the  horizontal  axle  m  m  and  gears  into  k. 

This  horizontal  axle  m  m  carries  at  one  of  its  ex- 
tremities one  crank  handle  n,  and  at  the  other  end 
a  fly-wheel  oo  which  regulates  the  motion.    One  of 


the  arms  of  the  fly-wheel  also  carries  a  handle  p, 
which,  if  desired,  may  be  used  for  turning  the  mill, 


HERMANN'S  MILL. 


629 


and  which  may  be  fixed  at  the  proper  radius  by  the 
nut  J. 

The  color  to  be  ground  is  placed  in  the  hopper  r 
opening  into  the  trough  s,  which  delivers  the  material 
into  the  opening  g  of  the  running  stone.  A  cord  or 
chain  t  is  wound  up  around  the  cylinder  v,  and 
presses  the  trough  s  against  the  square  shaft  h  which 
shakes  it  continually.  At  the  same  time  the  propor- 
tion of  material  delivered  is  regulated  by  raising  or 
lowering  s  by  means  of  the  cord  t.  The  winding 
cylinder  v  is  moved  by  the  handle  which  traverses  its 
extremity. 

A  copper  box  x  receives  the  ground  paint,  and  it 
is  carried  by  the  two  handles  z  z.  The  paint  may 
also  be  removed  from  this  box  by^  the  stopcock  t. 

Hermami^s  7nill. 

Mr.  Hermann,  of  Paris,  well  known  as  a  con- 
structor of  grinding  apparatus,  has  invented  a  new 
machine  for  grinding  paints  in  oil  and  in  water. 

Its  disposition  is  remarkably  simple,  and  consists 
of  an  eccentric  stone  of  granite  which  is  placed  in  a 
circular  trough  made  of  the  same  material  or  of  other 
hard  stone.  The  rotation  imparted  to  that  stone  pro- 
duces upon  the  materials  held  in  the  trough  a  circular 
and  eccentric  grinding,  which  constantly  displaces 
the  points  of  contact  of  the  rubbing  parts.  In  this 
manner  colors  and  other  products  may  be  pulverized 
and  ground  with  great  perfection. 


APPENDIX. 


THE  METRIC  SYSTEM  OF  WEIGHTS  AND  MEASURES. 

The  United  States  being  the  first  to  introduce  the  decimal 
systenn  into  the  coinage  of  the  country,  and  to  demonstrate  its 
superior  utility,  it  is  remarkable  that  we  have  hesitated  so  long 
in  regard  to  the  substitution  of  the  same  simple  and  rational 
system  of  weights  and  measures  for  the  complicated  and  con- 
fused standards  in  general  use. 

In  May,  1866,  the  Committee  on  Coinage,  Weights,  and  Mea- 
sures presented  to  the  House  of  Representatives  an  exhaustive 
report,  accompanied  by  bills  authorizing  the  introduction  of 
the  metric  system  into  the  various  departments  of  trade,  and 
making  all  contracts,  based  on  this  system  of  weights  and 
measures,  valid  before  any  court  in  the  United  States.  They 
said : — 

''THE  METRIC  SYSTEM. 

'*Tt  is  orderly,  simple,  and  perfectly  harmonious,  having  use- 
ful relations  between  all  its  parts.  It  is  based  on  the  meter, 
which  is  the  principal  and  only  arbitrary  unit.  Tiie  meter  is  a 
measure  of  length,  and  was  intended  to  be,  and  is,  very  nearly 
one  ten-millionth  of  the  distance  on  the  earth's  surface  from 
the  equator  to  the  pole.    It  is  39.37  inches,  very  nearly. 

'  The  are  is  a  surface  equal  to  a  square  whose  side  is  10 
meters.    It  is  nearly  four  square  rods. 

"  The  liter  is  the  unit  for  measuring  capacity,  and  is  equal  to 
the  contents  of  a  cube  whose  edge  is  a  tenth  part  of  the  meter. 
It  is  a  little  more  than  a  wine  quart. 

"The  gramme  is  the  unit  of  weight,  and  is  the  weight  of  a 
cube  of  water,  each  edge  of  the  cube  being  one  one-hundredth 
of  the  meter.    It  is  equal  to  15.432  grains. 
The  stere  is  the  cubic  meter. 

"Each  of  these  units  is  divided  decimally,  and  larger  units 
are  formed  by  multiples  of  10,  100,  &;c.  The  successive  mul- 
tiples are  designated  by  the  prefixes,  deka^  hecto^  kilo,  and  myria  ; 
the  subordinate  parts  by  deci,  centi,  and  milli,  each  having  its 
own  numerical  significance. 

"The  nomencluiure,  simple  as  it  is  in  theory,  and  designed 


632 


THE  METRIC  SYSTEM. 


from  its  origin  to  be  universal,  can  only  become  familiar  bj 
use.  Like  all  strange  words,  these  will  become  familiar  hy 
custom,  and  obtain  popular  abbreviations.  A  system  which 
has  incorporated  with  itself  so  many  different  series  of  weights, 
and  such  a  nomenclature  as  ^scruples,'  'pennyweights,'  'avoir- 
dupois,' and  with  no  invariable  component  word,  can  hardly 
protest  against  a  nomenclature  whose  leading  characteristic  is  a 
short  component  word  with  a  prefix  signifying  number.  We 
are  all  familiar  with  thermometer^  barometer^  diameter^  gasometer^ 
&c..  with  telegram^  monogram^  &c.,  words  formed  in  the  same 
manner. 

"  After  considering  every  argument  for  a  change  of  nomen- 
clature, your  committee  have  come  to  the  conclusion  that  any 
attempt  to  conform  it  to  that  in  present  use  would  lead  to  con- 
fusion of  weights  and  measures,  would  violate  the  early  learned 
order  and  simplicity  of  metric  denomination,  and  would  seri- 
ously interfere  with  that  universality  of  system  so  essential  to 
international  and  commercial  convenience. 

"  When  it  is  remembered  that  of  the  value  of  our  exports 
and  imports,intheyearending  June  30, 1860,  in  all  $762,000,000, 
the  amount  of  near  $700,000,000  was  with  nations  and  their  de- 
pendencies that  have  now  authorized,  or  taken  the  preliminary 
steps  to  authorize,  the  metric  system,  even  denominational  uni- 
formity for  the  use  of  accountants  in  such  vast  transactions 
assumes  an  important  significance.  In  words  of  such  universal 
employment,  each  word  should  represent  the  identical  thing  in- 
tended, and  no  other,  and  the  law  of  association  familiarizes  it. 

"Your  committee  unanimously  recommend  the  passage  of 

the  bills  and  joint  resolutions  appended  to  this  report  

The  metric  system  is  already  used  in  some  arts  and  trades  in 
this  country,  and  is  especially  adapted  to  the  wants  of  others. 
Some  of  its  measures  are  already  manufactured  at  Bangor,  in 
Maine,  to  meet  an  existing  demand  at  home  and  abroad.  The 
manufacturers  of  the  well-known  Fairbanks'  scales  state:  'For 
many  years  we  have  had  a  large  export  demand  for  our  scales 
with  French  weights,  and  the  demand  and  sale  are  constantly 
increasing.'  Its  minute  and  exact  divisions  specially  adapt  it 
to  the  use  of  chemists,  apothecaries,  the  finer  operations  of  the 
artisan  and  to  all  scientific  objects.  It  has  always  been  and  is 
now  used  in  the  United  States  coast  survey.  Yet  in  some  of 
the  States,  owing  to  the  phraseology  of  their  laws,  it  would  be 
a  direct  violation  of  them  to  use  it  in  the  business  transactions  of 
the  community.  It  is,  therefore,  very  important  to  legalize  its  use, 
and  to  give  to  the  people,  or  that  portion  of  them  desiring  it,  the 
opportunity  for  its  legal  employment,  while  the  knowledge  of 
its  characteristics  will  be  thus  difiused  among  men." 


TABLES 

SHOWING  THE 

RELATIVE  VALUES  OF  FRENCH  AND  ENGLISH  WEIGHTS 
AND  MEASURES,  &c. 


Measures  of  Length. 


Millimetre 
Centimetre 
Decimetre 
Metre 


Decametre 

Hectometre 

Kilometre 

Myriametre 

Inch  (Jg  yard) 
Foot  (i  yard) 
Yard 

Fathom  (2  yards) 
Pole  or  perch  (5^  yards) 
Furlong  (220  yards) 
Mile  (1760  yards) 
Nautical  mile 


0.03937 
0.393708 
3.937079 
39.37079 
3.2808992 
1.093633 
32.808992 
328.08992 
3280.8992 
1093.633 
10936.33 
6.2138 
2.539954 
3.0479449 
0.91438348 
1.82876696 
5.029109 
201.16437 
1609.3149 
1852 


inch. 

inches. 

feet. 

yard. 

feet. 
(( 

(( 

yards, 
miles. 

centimetres, 
decimetres, 
metre. 

metres. 


1 


634        VALUES  OF  FRENCH  AND  ENGLISH 

Superficial  Measures. 

square  inch. 
0.00155        "  " 
0.155006      "  " 
15.50059        "  inches. 
0.107643      "  foot. 
1550.05989        "  inches. 
10.764299      "  feet. 
1.19H033      "  yard 
1076.4299         "  feet. 
119.6033         «  yards. 
0.098845  rood. 
11960.3326     square  yards. 
2.471143  acres. 
645.109201  square  millimetres. 
6.451367      "  centimetres 
9.289968      "  decimetres. 
0.836097      "  metre. 
25.291939      "  metres. 
10.116775  ares. 
0.404671  hectare. 

Measures  of  Capacity. 


Cubic  millimetre 

0.000061027  cubic  inch. 

centimetre  or  millilitre 

0.061027 

(• 

10  " 

centimetres  or  centilitre 

0.61027 

((  (( 

100  " 

(( 

"  decilitre 

6.102705 

"  inches. 

1000  " 

it 

"  litre 

61.0270515 

«  (( 

a 

11  u 

1.760773 

imp'l  pint. 

((  (( 

u 

a  ii 

0.2200967 

"  gal'n. 

Decalitre 

610.270515 

cubic  inches, 

a 

2.2009668 

imp.  gal'ns. 

Hectolitre 

3.531658 

cubic  feet. 

22.009668 

imp.  gal'ns. 

Cubic  metre  or  stere  or  kilolitre 

1.30802 

cubic  yard. 

u 

35.3165807 

"  feet. 

Myrialitre 

353.165807 

((  (S 

Square  millimetre  = 

*'      centimetre  = 

"      decimetre  = 

((            ti  __ 

*'     metre  orcentiare  = 

t(         t(            ((  __ 

It  U  (( 

Are  = 

Hectare  = 

"  __ 

Square  inch  = 

«       «  __ 

"     foot  = 

"     yard  = 

"     lod  or  perch  = 

Rood  (1210  sq.  yards)  = 

Acre  (4840  sq.  yards)  = 


WEIGHTS  AND  MEASURES,  ETC. 


635 


Cubic  inch 
"  foot 
"  yard 


=  16.386176      cubic  centimetres. 

28.315312  "  decimetres. 

=     0.764513422     "  metre. 


American  Measures. 

WinchesterorU.S.  gallon  (231  cub.in.)      =      3.785209  litres. 

«  «    bushel(2150.42cub.in.)=     35.23719  " 

Chaldron  (57.25  cubic  feet)  =  1621.085  " 


British  Imperial  Measures. 

Gill  =  0.141983  litre. 

Pint  Q  gallon)  = 

Quart  (^  gallon)  = 
Imperial  gallon  (277.2738  cub.  in.)  = 

Peck  (2  gallons)  = 
Bushel  (8  gallons) 
Sack  (3  bushels) 


0.567932  « 
1.135864  " 
4.54345797  litres 
=  9.0869159  " 
=  36.347664  " 
==  1.09043 


Quarter  (8  busbels) 
Chaldron  (12  sacks) 


Milligramme 
Centigramme 
Decigramme 
Gramme 


Decagramme 

a 

Hectogramme 
(( 

Kilogramme 

a 

Myriagramme 


=  2.907813 
=  13.08516 


hectolitre, 
hectolitres. 


Weights. 

0.015438395  troy  grain. 
0.15438395     "  " 


1.5438395 
15.438395 
0.643 
0.0321633 
0.0352889 
l.'i4.38395 
5.64 
3.21633 
3.52889 
2.6803 
2.205486 
26.803 
22.05486 


"  grains, 
pennyweight, 
oz.  troy, 
oz.  avoirdupois, 
troy  grains, 
drachn^  avoirdupois, 
oz.  troy, 
oz.  avoirdupois, 
lbs.  troy, 
lbs.  avoirdupois, 
lbs.  troy, 
lbs.  avoirdupois. 


Quintal  metrique  = 
Tonne  = 


100  kilog.  =  220.5486  lbs.  avoirdupois. 
1000  kilog.  =  2205.486    "  " 


636 


TALUES  OF  FRENCH  AND  ENGLISH 


Different  authors  give  the  following  values  for  the  gramme  : — 
Gramme  =  15.44402    troy  grains. 
"         =  15.44242  " 
«        =  15.4402  « 
«        =  15.433159  " 
«        =  15.43234874  " 


AVOIRDUPOIS. 


Long  ton  =  20  cwt.  =  2240  lbs.  =  1015.649  kilogrammes. 


Short  ton  (2000  lbs.)  == 
Hundred  weight  (112  lbs.)  = 
Quarter  (28  lbs.)  = 
Pound  =  16  oz.  ==  7000  grs.  = 
Ounce  =  16  dr'ms.  =  437.5  grs.  = 
Drachm  =  27.344  grains  = 


906.8296 
50.78245 
12.6956144 

453.4148 
28.3375 
1.77108 


grammes. 


gramme. 


TROY  (precious  metals). 

Pound  =  12  oz.  =  5760  grs.  =  373.096  grammes. 

Ounce  =  20  dwt.  =  480  grs.  =  31.0913 

Pennyweight  =  24  grs.  s=      1.55457  gramme. 

Grain  =      0.064773  " 


APOTHECARIES'  (pharmacy). 

Ounce  =  8  drachms  =  480  grs.  =  31.0913  gramme. 
Drachm  =  3  scruples  =  60  grs.  =      3.8869  " 

Scruple  =•  20  grs.  =      1.29546  gramme. 


(?ARAT  WEIGHT  FOR  DIAMONDS. 

1  carat  =  4  carat  grains  =  64  carat  parts. 
"       =  3.2     troy  grains. 
«       =  3.273  "  " 
"       =  0.207264  gramme 
"       =  0.212  " 
=  0.205  " 
Great  diversity  in  value. 

4 


'     WEIGHTS  AND  MEASURES,  ETC.  637 

Proposed  Symbols  for  Abbreviations. 


M — myria  — 

10000 

Mm 

Mg 

Ml 

K— kilo  — 

1000 

Km 

Kg 

Kl 

H — hecto  — 

100 

Hra 

Hg 

HI 

Ha 

D — deca  — 

10 

Dm 

Dg 

Dl 

Da 

Unit  — 

1 

metre — m 

gramme — g 

litre— 1 

are — a 

d — deci  — 

0.1 

dm 

dg 

dl 

da 

c — centi  — 

0.01 

cm 

.  eg 

cl 

ca 

m — milli  — 

0.001 

mm 

mg 

ml 

Km  =  Kilometre.  HI  =  Hectolitre.  eg  =  centigramme, 
c.  cm  =  =  cubic  centimetre,  dm*  ==  sq.  dm  =  square  deci- 
metre.   Kgm  =  Kilogrammetre.    Kg°  =  Kilogramme  degree. 


Celsius  or  Centigrade. 

Fahrenheit. 

Rfeaumnr. 

—  15° 

+  5° 

—  12° 

—  10 

+  14 

—    8    '  . 

—  5 

+  23 

—  4 

0  melting 

+  32 

ice  0 

+  5 

+  41 

4-  4 

-f  10 

+  50 

+  8 

+  15 

+  59 

+  12 

4-  20 

+  G8 

+  16 

+  25 

+  77 

+  20 

4-  30 

+  86 

+  24 

+  35 

+  95 

+  28 

4-  40 

+104 

+  32 

4-  45 

+  113 

+  36 

4-  50 

+122 

+  40 

4-  55 

+  131 

+  44 

4-  60 

+140 

48 

4-  G5 

+149 

+.  52 

+  70 

+  158 

+  56 

+  75 

+  167 

+  60 

-f  80 

+176 

+  64 

+  85 

+185 

+  68 

+  90 

+194 

4-  72 

4-  95 

+203 

+  76 

+100  boiling 

+212 

water  +  80 

+200 

+  392 

+  160 

+  300 

+572 

+240 

+400 

+752 

+320 

+500 

+932 

+400 

5 


638 


VALUES  OF  FRENCH  AND  ENGLISH 


1°  C.  =  1°.8  Ft.  =  1°  Ft.  =  0°.S  R.  =  1°  R. 
1°  C.  X  f  =  1°  Ft.      1°  Ft.  X  f  =  1°  C.     1°  R.  X  f  =1°  Ft. 
1°  C.  X  ^  =  1°  R.       1°  Ft.  X  t  =  1°  R.     1°  R.  X  f  =1°  C. 

Calorie  (French)  =  unit  of  heat  ^ 

=  kilogramme  degree  /  ° 
It  13  the  quantity  of  heat  necessary  to  raise  1°  C.  the  tempera- 
ture of  1  kilogramme  of  distilled  water. 

Kilogrammetre  =  Kgra  =  the  power  necessary  to  raise  1  kilo- 
gramme, 1  metre  high,  in  one  second.  It  is  equal  to  -^^  of  a 
French  horse  power.  An  English  horse  power  =  550  foot  pounds, 
while  a  French  horse  power  =  542.7  foot  pounds. 


Ready-made  Calculations. 


No. 

of 

Inches  to 

Feet  to 

Yards  to 

Miles  to 

Millimetres 

units. 

centimetres. 

metres. 

metres. 

Kilometres. 

to  inches. 

1 

2.53995 

0.3047945 

0.91438348 

1.6093 

0.03937079 

2 

5.0799 

0.6095890 

1.82876696 

3.2186 

0.07874158 

3 

7.6199 

0.9143835 

2.74315044 

4.8279 

0.11811237 

4 

10.1598 

1.2197680 

3.65753392 

6.4373 

0.15748316 

5 

12.6998 

1.5239724 

4.57191740 

8.0466 

0.19685395 

6 

15.2397 

1.8287669 

5.48630088 

9.6559 

0.23622474 

7 

17.7797 

2.1335614 

6.40068436 

11.2652 

0.27559553 

8 

20.3196 

2.4383559 

7.31506784 

12.8745 

0.31496632 

9 

22.8596 

2.7431504 

8.22945132 

14.4838 

0.35433711 

10 

25.3995 

3.0479450 

9.14383480 

16.0930 

0.39370790 

No. 

Centimetres 

Metres  to 

Metres  to 

Kilometres 

Square  inches 

of 

to  inche». 

feet. 

yards. 

to  miles. 

to  square 

nnits. 

centimetres. 

1 

0.3937079 

3.2808992 

1.093633 

0.6213824 

6.45136 

2 

0.7874158 

6.5617984 

2.187266 

1.2427648 

12.90272 

3 

1.1811237 

9.8426976 

3.280899 

1.8641472 

19.35408 

4 

1.5748316 

13  1235968 

4.374532 

2.4855296 

25.80544 

5 

1.9685395 

16.4044960 

5.468165 

3.1089120 

32.256S0 

6 

2.3622474 

19.6853952 

6.561798 

3.7282944 

38.70816 

7 

2.7559553 

22.9662944 

7.655431 

4.3496768 

45.15952 

8 

3.1496632 

26.2471936 

8.749064 

4.9710592 

51.61088 

9 

3.5433711 

29.5280928 

9.842697 

5.5924416 

58.06224- 

10 

3.9370790 

32.8089920 

10.936330 

6.2138240 

64.51360 

6 


WEIGHTS  AND  MEASURES,  ETC. 


639 


No. 

OC[URl'6  IGGt  to 

yfirds  to 

Acres  to 

oquare 

of' 

sq.  metres. 

sq.  metres. 

hectares. 

centimetres 

to  sq.  feet. 

units. 

to  sq,  inches. 

1 

0.0929 

0.836097 

0.404671 

0.155 

10.7643 

2 

0.1858 

1.672194 

0.809342 

0.310 

21.5286 

3 

0.2787 

2.508291 

1.204013 

0.465 

32.2929 

4 

0.3716 

3.344388 

1.618684 

0.620 

43.0572 

5 

0.4645 

4.180485 

2.023355 

0.775 

53.8215 

6 

0.5574 

5.016582 

2.428026 

0.930 

64.5858 

7 

0.6503 

5.852679 

2.832697 

1.085 

75.3501 

8 

0.7432 

6.688776 

3.237368 

1.240 

86.1144 

9 

0.8361 

7.524873 

3.642039 

1.395 

96.8787 

10 

0.9290 

8.360970 

4.046710 

1.550 

107.6430 

No. 

Square  metres 

Hectares 

Cubic  inches 

Cubic  feet  to 

Cubic  yards 

of 

to  sq.  yards. 

to  acres. 

to  cubic 

cubic  metres. 

to  cubic 

units. 

centimetres. 

metres. 

1 

1.1960.33 

2.471143 

16.3855 

0.02831 

0.76451 

2 

2.392066 

4.9422S6 

32.7710 

0.05662 

1.52902 

3 

3.588099 

7.413429 

49.1565 

0.08494 

2.29354 

4 

4.784132 

9.884572 

65.5420 

0.11325 

3.05805 

5 

5.980165 

12.355715 

81.9275 

0.14157 

3.82257 

6 

7.176198 

14.826858 

98.3130 

0.16988 

4.58708 

7 

8.372231 

17.298001 

114.6985 

0.19819 

5.:^5159 

8 

9.568264 

19.769144 

131.0840 

0.22651 

6.11611 

9 

10.764297 

22.240287 

147.4695 

0.25482 

6.88062 

10 

11.960330 

24.711430 

163.8550 

0.28315 

7.64513 

No. 

Cubic 

Litres  to 

Hectolitres  to 

Cubic  metres 

Cubic  metres 

of 

centimetres  to 

cubic  inches. 

cubic  feet. 

to  cubic  feet. 

to  cubic 

units. 

cubic  inches. 

yards. 

1 

0.06102 

61.02705 

3.5317 

35.31659 

1.30802 

2 

0.12205 

122.05410 

7.0634 

70.63318 

2.61604 

3 

0.18308 

183.08115 

10.5951 

105.94977 

3.92406 

4 

0.24411 

244.10820 

14.1268 

141.26636 

5.23208 

5 

0.30514 

3<>5.13525 

17.6585 

176.58295 

6.54010 

6 

0.36617 

366.16230 

21.1902 

211.89954 

7.84812 

7 

0.42720 

427.18935 

24.7219 

247.21613 

9.15614 

8 

0.48823 

488.21640 

28.2536 

282.53272 

10.46416 

9 

0.54926 

549.24345 

31.7853 

317.84931 

11.77218 

10 

1 

0.61027 

610.27050 

35.3166 

353.16590 

13.08020 

7 


640      FRENCH  AND  ENGLISH  WEIGHTS,  ETC. 


No. 

■  Grains 

Ounces  avoir. 

Ounces  troy 

Pounds  avoir. 

Pounds  troy 

of 

to  grammes. 

to  grammes. 

to  grammes. 

to 

to 

kilogrammes,  kilogrammes. 

1 

0.064773 

28.3375 

31.0913 

0.4534148 

0.373096 

2 

56  6750 

62  1826 

0.9068296 

0.746192 

3 

0.194319 

85.0125 

93.2739 

1.3602444 

1.119288 

4 

0.259092 

113.3500 

124.3652 

1.8136592 

1.492384 

5 

0.323865 

141.6871 

155.4565 

2.2670740 

1.865480 

6 

0.388638 

170.0250 

186.5478 

2.7204888 

2.238576 

7 

0.453411 

198.3625 

217.6391 

3.1739036 

2.611672 

8 

0.518184 

226.7000 

248.7304 

3.6273184 

2.984768  ■ 

9 

0.582957 

255.0375 

279.8217 

4.0807332 

3.357864  ' 

10 

0.647730 

283.3750 

310.9130 

4.5341480 

3.730960 

Pounds  per 

No. 

Lone  tons  to 

square  inch  to 

Grammes  to 

Grammes  to 

Grammes  to 

of 

tonnes  of  1000  kilogrammes 

grains. 

ounces  avoir. 

ounces  troy. 

units. 

kilog. 

per  square 
centimetre. 

1 

1.015649 

0.0702774 

15.438395 

0.0352889 

0.0321633 

2 

2.031298 

0.1405548 

30.876790 

0.0705778 

0.0643266 

3 

3.046947 

0.2108322 

46.315185 

0.1058667 

0.0964899 

4 

4.062596 

0.2811096 

61.753580 

0.1411556 

0.1286532 

5 

5.078245 

0.3513870 

77.191975 

0.1764445 

0.1608165 

6 

6.093894 

0.4216644 

92.630370 

0.21173.^4 

0.1929798 

7 

7.109543 

0.4919418 

108.068765 

0.2470223 

0.2251431 

8 

8.125192 

0.5622192 

123.507160 

0.2823112 

0.2573064 

9 

9.140841 

0.6324966 

138.945555 

0.3176001 

0.2894697 

10 

10.156490 

0.7027740 

154.383950 

0.3528890 

0.3216330 

No. 
of 
units. 

Kilogrammes 

to  pounds 
avoirdupois. 

Kilogrammes 
to  pounds 
troy. 

Metric  tonnes 
of  1000  kilog 
to  iong  tons  of 
2240  pounds. 

Kilog.  per 
square  milli- 
metre to 
pounds  per 
square  inch. 

Kilog.  per 
square  centi- 
metre to 

pounds  per 
square  inch. 

1 

2.205486 

2.6803 

0.9845919 

1422.52 

14.22526 

2 

4.410972 

5.3606 

1.9691838 

2845.05 

28.45052 

3 

6.616458 

8.0409 

2.9537757 

4267.57 

42.67578 

4 

8.821944 

10.7212 

3.9383676 

5690.10 

56.90104 

5 

11.027430 

13.4015 

4.9229595 

7112.63 

71.12630 

6 

13.232916 

16.0818 

.^.9075514 

8535.15 

85.35156 

7 

15.438402 

18.7621 

6.8921433 

9957.68 

99.57682 

8 

17.643888 

21.4424 

7.8767352 

11380.20 

113.80208 

9 

19.849374 

24.1227 

8.8613271 

12802.73 

128.02734 

10 

22.054860 

26.8030 

9.8459190 

14225.26 

142.25260 

INDEX. 


ABSORBED  colors,  46 
Acetate  of  lead,  158 
Ador  and  Abadi^,  colors  of  sulphate  of 

zinc  by,  574-577 
Adulteration  of  zinc  white,  189,  190 

of  zinc  yellows,  391 
Adulterations  of  lakes,  471 
Air  furnace,  178 

Aldobrandini  wedding,  blues  in,  29 

browns  used  in  the,  20 

greens  of,  32 

reds  of,  22 

yellows  of,  21 
Alexandria  frit,  35 
Algaroth  powder,  163-164 
Alizari,  458 

Alkalies,  effect  of  Prussian  blue  on,  202 
Alkalized  charcoal,  preparation  of,  222, 

223,  224,  225 
Alkanet,  474 

Alumina,  addition  of,  to  chromates,  376 

for  artificial  ultramarine,  290 
Aluminous  silicate,  306 
Alum,  resistance  of  ultramarine  to, 

333 

American  measures,  635 
Ammonia  and  hydrated  oxide  of  copper, 
350 

transformation  of,  into  cyanide  of 
ammonium,  210 
Ammoniacal  cochineal,  494 

sulphate  of  copper,  349 
Analyses  of  Indian  yellow,  418,  419 

of  iron  minium,  502 

of  ultramarine,  272 

of  white  lead,  76,  77,  132,  137 
Analysis  of  artificial  ultramarine,  296- 
297 

of  cochineal,  487 

of  Cologne  yellow,  377 

of  copper  blues,  347-349 

of  curcuma,  365 

of  green  without  arsenic,  548 


Analysis — 

of  lazulite,  272-273 

of  luteolin,  370,  371  . 

of  purple  of  Cassius,  456-457 

of  Rinmann  green,  560 

of  silicious  sand,  290 

of  sulphide  of  antimony,  444-445 

of  ultramarines,  276,  329-339 

of  white   lead  made   by  Wood, 
Benson,    and   Griineberg  pro- 
cesses, 102 
Analytical  operation  with  ferrocyanide 

of  potassium,  234 
Ancients,  colors  employed  by  the,  17 
Aniline  or  chrome  black,  524 
Animal  blacks,  529-532 

substances,  ferrocyanide  of  potass- 
ium with,  223-236 
Annales  des  Arts  et  Manufactures,  165 
Anthon,  C.  F.,  process  for  the  manu- 
facture of  uranium  yellow,  412 
Antimoniate  of  lead,  161,  400 
Antimonite  of  lead,  160 
Antimony  and  zinc,  yellow  of,  401-403 

chloride  of,  446 

orange-red  sulphide,  392-393 

oxide  of,  161,  401 

protochloride  of,  443 

sulphide  of,  441 

compound  colors  with,  393 

vermilion  of,  441 

white  less  affected  by  sulphuretted 
hydrogen  than  white  lead, 
164 

of  Bobierre,  Ruolz,  and  Rous- 
seau, 161-162 
of  Hallett  and  Stenhouse,  164 
of  Vall6  and  Barreswill,  162- 
164 

whites,  161-164 
yellow,  358,  394,  405 
Antwerp  blue,  256-257 
red,  362 


41 


642 


INDEX. 


Apparatus,  absorbing,  215-217 

Crompton's,  for  white  lead,  115-123 
for  manufacture  of  oxide  of  zinc, 

169-180 
for  oxide  o^  antimony,  161 
Mullin's,  for  white  lead',  106-110 
of  C,  Schinz  for  ferrocyanide  of 

potassium,  226 
of  M.  Ozouf  for  preparation  of 

white  lead,  154 
of  Th.   Lefevre   for  pulverizing 

white  lead,  140-145 
of  Versepuy,  95-96 
Sewell's,  for  white  lead,  113-114 
Ward's,  for  manufacture  of  white 

lead,  138-140 
Wood's,  for  white  lead,  98 
Archil,  coloring  principles  of,  498 
-lichens,  496 
red  and  violets  from,  495 
Armenian  bole,  425 

stone,  351 
Arnatidon,  Mr.,  process  for  emerald 

green,  566 
Arseniate  of  cobalt,  455 
Arsenite,  neutral,  of  copper,  543 
of  copper,  341 
of  lead,  409 
Artificial  flowers,  green  for,  537 
sulphate  of  baryta,  193-199 
ultramarine,  274-340 
Ashes,  blue,  341-351 

manufacture  of,  in  England, 
342 

green,  548 
Asphaltum,  509-510 
qualities  of,  510 
Atkinson,  Mr.,  of  Harrington,  patent  of, 

for  zinc  white,  in  1796,  165 
Atomic  sulphate,  190 
Aurum  mussivum,  420-421 
Avignon  berries,  358,  366 
Azure  blue,  351 

inconvenience  of  using,  354 
lazulite,  270 
tint  of,  185 
white,  185-203 
Azurite,  350 


BA.CCO,  A.,  process  for  removing  iron 
from   solutions  of  sulphate  of 
copper,  547 
process  for  testing  white  leads, 
133-134 

Baker,  W.,  on  composition  of  Holland 

white  lead,  135 
Balls  of  wuy,  357 

Bancroft,  Dr.  Edward,  on  Tyrian  pur- 
ple, 25 


Barium,  chloride  of,  197 

sulphide  of,  197 

sulpho-antimonite  of,  453-454 
Baroselenite,  192 

Barreswill,  Mr.,  on  the  value  of  ultra- 
marine, 338,  339 

Barruel  and  Leclaire,  Rinmann  green 
of,  560 

Baryta,  chromate  of,  378-379,  391-392 
compound  colons  with,  393 
in  zinc  yellow,  391 
sulphate  of,  192-199 

in  white  lead,  132,  133 
to  detect  in  white  lead,  133 
white,  132 
whites,  192-199 
yellow,  169 
Barytes,  sulphates  of,  192-199 
Barytine,  192-199 
Basic  acetate,  81 

chloride  of  lead,  158-159 
chromate,  385-386 
of  lead,  375-376 
of  tin,  395 
of  zinc,  394 
Baths  of  Livia,  browns  used  in  pictures 
of,  20 
green  color  in,  30 
of  Titus,  17,  20,  22,  23,  36 
Beds  for  white  lead,  147,  148 
Benson's  process  for  white  lead,  97- 
105 

Berlin  brown  red,  406 
Berzelius  on  the  composition  of  indigo, 
267 

Besanyon,  M.,  apparatus  for  grinding 

white  lead  in  oil,  152 
Bichromate  of  potassa,  388 
Bi-iodide  of  mercui'y,  439 
Binary  colors,  48 

mixed  colors,  48 
Bistre,  508 

deep,  52 
Bisulphide  of  arsenic,  429 
Bitumen,  drying,  preparing,  510 

naphtha,  509 

of  Judea,  509 

qualities  of,  510 
Bitumens,  509-510 
Bituminous  coal  black,  514-515 
Black  absorbs  all  colors,  37 

aniline  or  chrome,  524 

bituminous  coal,  514-515 

Campeachy  lakes,  475 

candle,  530 

charcoal,  516,  525 

cork,  516 

Frankfort,  516 

fusain,  515 

German,  516 


INDEX. 


643 


Black- 
grape-vine,  515 
ivory,  530 
lakes,  474 

of  chromate  of  copper,  514 
peach  stone,  515 
Prussian,  531 
shale,  512-518 
sumach  lake,  475 
Blacks,  512-532 

animal,  529-532 
artificial,  of  Greece,  19 
bone,  529 
ebony,  515 

from  Prussian  blue  ground  in  oil,  203 
mineral,  512-514 
ulmin,  525 

used  by  the  Egyptians  and  Romans, 
19 

vegetable,  515,  625,  526 
Blanc  fixe,  132,  193,  199 
Blende,  177,  178 

as  a  substitute  for  white  lead  and 
zinc  white,  191-192 
Blood  lye,  201,  240 

use  of,  in  manufacture  of  Prussian 
blue,  201 
Blue,  ancient,  analysis  of,  29 
arsenite  of  copper,  341 
ashes,  341-351 

for  painted  papers,  342 
French  and  English,  350 
in  paste,  345-347 
L.  G.  Gentele  on  the  prepara- 
tion of,  345 
of  the  manufacturers,  341 
Pelletier  on  the  preparation 
of,  341 
azure,  351 
Bremen,  538-548 
calcareous,  345 
carmine,  268-269 
celestial  or  Marie  Louise,  51 
color  of  ultramarine,  intensity  of, 
321 

colors,  199-357 
composition,  268 
copper,  341-351 
English  sky,  356-357 
from  an  Egyptian  grave,  27 
green,  345 

hydrated  oxide  of  copper,  261 
in  liquor,  268 
lime,  341-351 
made  at  Pozzuoli,  30 
mineral  or  Antwerp,  256-257 
Monthiers,  253 
mountain,  341-351 
of  England,  268-269 
of  Holland,  268-269 


Blue— 

of  manganate  of  lime,  262-264 
of  white  earths,  colored  with  in- 
digo, 257 
Paris,  244-253 
P^ligot,  261 
Saxony,  351 
sky,  203 
smalt,  351 

Th^nard  or  cobalt,  257-261 
tint  of  azure,  185 
Turnbull's,  244 

ultramarine,Gentele's  processes  for, 
318-323 

verditer,  538-543 
Blues  at  Pompeii,  29 

in  the  Aldobrandini  Wedding,  29 

most  frequently  used,  199 

of  the  ancients,  26 

ultramarine,  269-340 
Bluing  agent  of  ultramarine  green,  323 
Bobierre,  Ruolz,   and  Rousseau,  anti- 
mony white  of,  161-162 
Boilers,  painting  with  iron  minium,  504 
Bole,  425 

Bologna  stone,  192 
Bolus  alba,  283 
Bone-blacks,  529 

Bone-black,  use  of  in  manufacture  of 

Prussian  blue,  243 
Borate  of  cobalt,  584 

of  manganese,  585 
Boric  acid  as  a  solvent,  563 
Bouchard  and  Clavel,  MM.,  experiments 

on  Burgundy  ochre,  501 
Bouland,  Mr.,  process  for  green  ochre, 

571 

Bourgeois,  Mr,,  on  purity  of  tones  of 

Prussian  blue,  202 
Bouton  d'or  yellow,  169 
Boutron-Chartard,  analysis  of  Cologne 

yellow  by,  377 
Bouvier,  Mr.,  process  for  the  manu- 
facture of  Prussian  brown,  506 
Braconnot,  Mr.,  process  for  Schweinfurt 

green,  546 
Brazil  wood,  lakes  of,  472 
Bremen  blue,  345,  347,  350,  538,  543 

green,  538-543 
Bright  yellow,  394 
British  imperial  measures,  635 
Broken  or  pure  colors,  39 
Bronze  coloration  without  lampblack, 
601 
colors,  575 

dark,  575 
compositions  for  metals,  595-5S>9 
^    -green,  185,  563 

ordinary,  of  the  founders,  599 
red,  594 


644 


INDEX. 


Bronzing,  593-603 

for  gunbarrels,  601 
naixtures,  mode  of  applying,  699- 
601 

plaster  of  Paris,  601 
Brown,  chicory,  507 
colors,  500-512 
gilt,  507 

manganese,  505-506 
Mars,  423,  500,  501 

from  Mars  yellow,  500 
of  manganate  of  lead,  506 
of  the  Aldobrandini  Wedding,  20 
Prussian,  506 
red,  507 

Berlin,  406 
ulmin,  507-508 
Van  Dyke,  504-505 
Browns  used  by  the  Egyptians  and  Ro- 
mans, 19 
Brumlen,  L.,  of  New  York,  188 
Brunner,  Mr.,  on  the  preparation  of 
Naples  yellow,  398 
on  preparation  of   native  ultra- 
marine, 271 
process  for  artificial  ultramarine, 
289-300 

process  for  preparing  vermilion, 
432-433 
Brunnquell,  Mr.,  230,  254 

process  for  ferrocyanide  of  potass- 
ium, 205-219 
for  Prussian  blue,  205-219 
Brunswick  green,  543 
Brussels  lace,  zinc  white  in  manufacture 

of,  168 
Buccina,  purple  from,  26 
Biichner,  W.,  on  testing  ultramarines, 

333-338 
Buckthorn  berries,  536 
Building  the  beds  for  white  lead,  147 
Burgundy  ochre  as  a  substitute  for  red 
lead,  601 


CADMIUM  yellow,  400-401 
Caius  Cestus,  blue  in  the  monu- 
ment of,  at  Rome,  29 
Calcareous  blue,  345 
Calcination,  312-313,  315,  319,  321 
French,  321-322 
of  Prussian  blue,  243 
Calcining  furnaces,  313-315 
Calcium,  chloride  of,  85 

hyposulphite  of,  447 
Calculations,  ready  made,  638 
Calico  printing,  ultramarines  for,  330 
Campeachy  black,  475 

lakes,  473 
Candle  black,  530 


Capacity,  measures  of,  634 
Carbon,  309 

Carbonate  of  copper,  341 
of  lead,  condensing,  115 

by  the  Pattinson  process,  85- 

92 

production  of,  110 
of  lime,  53,  54,  85,  86 

in  white  lead,  128 
of  soda,  for  artificial  ultramarine, 
291 

for  ultramarine  green,  308 
washing  white  lead  in,  116 
Carbonic  acid,  absorption  of  by  granu- 
lated lead,  93 
for  manufacture  of  white  lead, 
60 

for  white  lead,  83 
production  of,  112 
Carbonizing  furnaces,  213 
Carmine,  blue,  268-269 
cochineal,  487-493 
lake,  473,  493 
madder,  473,  477 
Carthamic  acid,  484 
Carthamin,  484 
Carthamus  red,  484 
Cartret,  Mr.  de,  iron  minium  prepared 

by,  425 
.Cassel  earth,  512 

yellow,  403 
Cassius,  purple  of,  456-468 
Casting  of  lead,  146 
Cat's  gold,  420-421 
Celestial  blue,  51 

Certeau,  Mr.  de,  on  the  use  of  blende, 

191,  192 
Chalk  in  white  lead,  128 
Chalk  whites,  53-54 
Chamois,  185 
dark,  576 

hues  from  chrome  yellows,  377 
yellows,  574 
Chaptal,  17 

Chaptal,  Mr.,  process  for  Turner  yellow, 
403 

Chaptal's   examination   of  the  paint 

found  in  Pompeii,  32 
Charcoal,  alkalized,   222,    223,  224, 

225 

and  lampblack,  474 

black,  516,  526 

for  artificial  ultramarine,  291 
Chateau,  T.,  on  madder  and  its  deriva- 
tives, 471 
Chevreul,  Mr,,  on  colors,  39-49 

on  composition  of  indigo,  266 
Chicory  brown,  607 
China  green,  554-556 
China  or  India  ink,  531 


INDEX. 


645 


Chinese  process  for  cochineal  carmine, 
490 
rouge,  484 
Chloride  of  antimony,  446 
of  calcium,  85 
of  lead,  158-159 
of  manganese,  economy  of,  194 
Chlorine  manufacture,  utilization  of  the 

residue  of,  197 
Chlorophyl,  421-422 
Chocolate  lake,  475,  476 
Chromate,  basic,  385-386 
of  lead,  375-376 
of  tin,  395 
of  zinc,  394 
dense  neutral,  of  lead,  Liebig's 
process  for  manufacture  of,  374 
neutral,  373 

of  lead,  373-375 
of  soda  and  potassa,  388 
of  baryta,  378-379 

compound  colors  with,  395 
of  copper,  440 

black  of,  514 
of  lime,  378 

of  manganese,  puce  color  with,  512 

of  silver,  440 

of  zinc,  analysis  of,  391 

compound  colors  with,  395 
green  from,  388 
preparation  of,  387-391 
preparations,    materials  for, 

390 
washing,  390 
Chromates  of  mercury,  439,  440 
potassa,  373 
various,  387-395 
Chromatic   circles   of  Mr.  Chevreul, 
39-45 

Chrome  green,  561-563 

greens,  by  mixture,  386-387 
or  aniline  black,  524 
red,  382,  385-387,  500 

hues  of,  385 
yellow,  358,  379-385,  394 

hues  of,  382 

Jonquil,  of  Winterfeld,  376- 

377 
tones  of,  383 
yellows,  372-387 

adulterations  of,  378,  379 
brightness  and  durability  of, 
377 

Chromium,  372 

combinations  of,  in  the  arts,  372 

perchloride  of,  499-500 

sesquioxide,  561 
Chrysocolla,  31 
Cicerculum,  19 
Cinnabar,  430-439 


Cinnabar — 

discovery  of,  in  Rome,  28 

green,  246,  386,  553 

in  India,  21 
Classification  of  colors,  48-49 
Clay  for  artificial  ultramarine,  283 

for  ultramarine,  302 

porcelain,  306 
Clement  and  Desormes'  analysis  of  ul- 
tramarine, 272 
Clichy  process,  78-85 

whites,  55-56 
Coal  black,  bituminous,  514-515 
Cobalt,  arseniate  of,  455 

benzoate  of,  583 

blue,  257-261 

borate  of,  584 

glass,  351 

green,  556-561 

ore,  351 

pink,  454 

subphosphate  of,  257 

ultramarine,  340 
Cochineal,  487 

ammoniacal,  494 

analysis  of,  487 

carmine,  487-493 
Cochois,  Mr.,  preparation  of  ochres  by, 
360 

Coeruleum,  354-356 

advantages  of,  354 

composition  of,  355 

imitation,  356 
Coke  oven,  178 
Colcothar,  424,  426 

disadvantages  of  use  of,  on  iron, 
503 

Cologne  earth,  512 

yellow,  358,  377-378 
Coloring  power  of  ultramarine,  trial  of, 
334 

principles  of  archil,  498 
Color  of  smalt,  351 
Colors,  absorbed,  46 

binary,  48 

mixed,  48 

classification  of,  48-49 

complementary,  46 

contrast  of,  47 

employed  by  the  ancients,  17 
English  mill  for  grinding,  626 
from  sulphate  of  zinc,  574-577 
general  method  of  preparing,  49- 
52 

juxtaposited     and  compounding 

complementary,  47 
mill  for  grinding,  604-607 
mixed  or  compound,  393-395 
mixing,  394 
normal,  37 


646 


INDEX. 


Colors — 

of  the  rays  of  the  solar  spectrum,  46 

oils,  and  varnishes,  Bessemer  and 
Heywood's  improvements  in  the 
manufacture  of,  608-629 

origin,  definition,  and  classification 
of,  37-52. 

physical  effects  of,  46-48 

primary,  37,  46,  48 

rays  reflected  by,  37 

tertiary,  49 

those  in  use  among  the  ancients,  36 
Combes,  R.,  on  Holland  process,  64 
Complementary  colors,  46 
Composition  blue,  268 

of  ultramarines,  389-340 

of  white  lead,  134-137 
Compound  colors,  393-395 
Contrast  of  colors,  47 

modification  of,  47 

nature  of,  48 

of  tone,  46 
Copper,  ammoniacal  sulphate  of,  349 

arsenite  of,  341 

black  of  chromate  of,  514 

blue,  341-351 

hydrated  oxide  of,  261 

carbonate  of,  351 

..chromate  of,  440 

colors,  L.  G.  Gentele  on  the  pre- 
paration of,  345 
fine  commercial  white  lead  should 

be  free  from,  104 
green  of  stannate  of,  552 
hydrated  oxide  of,  538 
and  ammonia,  350 
oxide,  impairs  colors  of  white  lead 
paints,  105 
Copperas,  424 
Cork  black,  516 

Courtois,  early  manufacture  of  zinc 
white  by,  165 
of  Dijon,  mention  of  zinc  white  by, 
in  1770,  164 
Cream  tartar  process  for  cochineal  car- 
mine, 491 

Crompton's  apparatus  for  white  lead, 
115-123 

patents,  claims  under,  123-125 

process  for  white  lead,  115-125 
Crucibles  for  ultramarine,  313 
Crystallized  ferrocyanide  of  potassium, 
use  of,  243 

verdet,  573 
Crystals  of  Venus,  573 
Curcuma  longa,  364 

rotunda,  364 
Cyanide  lye,  202,  203 

of  ammonium,  210,  215 

of  potassium,  215 


DARK  chamois,  185 
English  green,  169,  394 
Davy,  Sir  Humphry,  17,  18,  19,  20,  21, 
22,  23,  24,  25,  31,  32,  34, 

36 

a  blue  color  in  imitation  of  the 

Egyptian,  made  by,  28 
on  the  blue  of  the  ancients,  28 
Deep  bistre  color,  52 

green  color,  51 
Definition  of  colors,  39-45 
Desbach,  of  Berlin,  discovery  of  Prus- 
sian blue  by,  199 
Desmotte's,  Mr.,  process  for  vermilion 

unalterable  by  fire,  438 
Desmoulin's  process  for  brightening  the 

color  of  vermilion,  437 
Determination  and  definition  of  colors, 
39-45 

of  the  value  of  the  fused  materials 
in  the  manufacture  of  ferrocya- 
nide of  potassium,  230-235 
Digeon,  Mr.,  engravings  of  chromatic 

circles  of  Mr.  Chevreul,  41-45 
Dippel,  J.  P.,  on  comparing  ultrama- 
rines, 330 
process  for  artificial  ultramarine, 
300-301 
Distilled  green,  573 

Dryer,  benzoates  of  cobalt  and  of  man- 
ganese, 583 

borate  of  manganese  as  a,  585 

for  zinc  white,  578 

of  borate  of  cobalt,  584 

powdered,  of  Guynemer,  579 
Dryers,  Mr.  Lefort  on,  188,  189 

resins  as,  584 

various,  580-588 
Dry  grinding  scales  of  white  lead,  149 
Drying  and  adherence  of  colors,  577- 
593 

oils,  578 

oil  with  peroxide  of  manganese, 

169 
rooms,  150 
Dumas  and  le  Royer  on  the  composi- 
tion of  indigo,  267 
Mr.,  on  red  lead,  426 
Dussauce,  Prof.,  on  a  new  vegetable 

red,  486 
Dutch  process,  55,  63,  78 


EBELMEN,  researches  of,  on  artificial 
production  of  mineral  compounds, 

563 

Ebony  black,  515 

Economy  in  the  manufacture  of  ferro- 
cyanide of  potassium,  210,  218,  226, 
229 


INDEX. 


647 


Egyptian  pictures,  colors  used  in,  18 
Egyptians  and  Romans,  whites  used  by, 
17 

reds  used  by,  21 
Elderberries,  475-476 
Eisner  and  Varrentrapp,   analysis  of 
ultramarine,  by,  275 

green,  553 

L.,  process  for  green  cinnabar,  553 
process  for  titanium  green,  568 
Emerald  gi-een,  563-568 
Enamel  blue,  351 

Encyclopedic  methodique  des  arts  et 

metiers,  164 
England,  manufacture  of  blue  ashes 
in,  342 

manufacture  of  white  lead  in,  69,  72 
English  green,  169,  394,  550 

process   for  the  manufacture  of 
Prussian  blue,  239-244 

red  or  rouge,  424 

sky  blue,  356-357 
Erlaa  green,  549 
Eschel  blue,  353 
Euxanthic  acid,  418 
Extract  of  Saturn,  60,  78 

FERROCYANIDE  of  potassium,  203 
economy  in  the  manufacture 

of,  210,  218,  226,  229 
from  horn,  224,  225 
furnace  for,  206 
manufacture  of,  205-219 
obtained  with  Karmrodt's  fur- 
nace, 223 
Schifiz's  process,  226-230 
testing,  234 

transformation  of  cyanide  of 
potassium  into,  215 

value  of  the  fused  materials  in 
the  manufacture  of,  230-235 

with  animal  substances,  223- 
226 

yielded  by  various  substances, 
220 

Ferrugine  aluraineuse,  501 
Firmenich  process  for  preparing  ver- 
milion, 434-437 
Flame  receiver,  Crompton's,  117 
Flat  lake  of  Italy,  478 
Flea  color,  512 

Fleck,  Mr.,  on  proportions  of  materials 
for  ferrocyanide  of  potassium,  231 

Flowers  of  zinc,  181 

Fougeroux  de  Bondaroy,  on  the  prepara- 
tion of  Naples  yellow,  397 

France,  early  manufacture  of  zinc  white 
in,  165 

Frankfort  black,  516 


Freray,  Mr.,  researches  on  the  green 

coloring  matter  of  leaves,  421-422 
French  and  English  weights  and  mea- 
sures, 633-640 
color  trade,  white  of,  composition 
of,  133 

encyclopedia,  process  for  cochineal 

carmine,  489 
process  for  white  lead,  78-85 
Fresco  paintings,  ancient,  18,  21,  29 
Frit,  Alexandria,  35 
Furnace  for  cyanide  of  potassium,  206 
Karmrodt's,  for  cyanide  of  potas- 
sium, 220-222 
Furnaces,  178 

calcining,  313-315 
carbonizing,  213 
for  zinc,  169-175 
Furstenau  process  for  ultramarine,  323- 
327 

Fusain  black,  515 


GALENA,  heating  of,  90 
Gamal  process  for  white  lead,  125, 
126 

Gamboge,  417 

Gamuts,  broken,  of  Mr.  Chevreul,  44 
of  colors,  Mr.  Chevreul,  42-45 
pure,  of  Mr.  Chevreul,  42,  44 

Garanceux,  lake  of,  467-468 

Garancin,  458,  459,  463,  465,  466 

Gases  from  bituminous  coal,  purifica- 
tion of,  115 

Gaultier  de  Claubry,  Mr.  H.  on  red 
and  violet  from  archil,  495 

Gelatine,  trial  for  the  proportion  of  for 
ultramarine,  337-338 

General  method   of  preparing  colors, 
49-52 

Gentele,  L.  G.,  on  the  preparation  of 
copper  colors,  345 
on  the  proportions  of  materials  for 

ferricyanide  of  potassium,  231 
processes  for   artificial  ultrama- 
rine, 304-323 
German  black,  516 

green  without  arsenic,  548 
process  for  cochineal  carmine,  491 
Giallolini,  397 
Gilt  brown,  507 

Girardine,  Mr.,  analysis  of  an  ancient 
blue,  29 

Glazing  power  of  ultramarine,  trial  of, 

337 

Glue  size,  yellow  ochre  with,  361 
Glycerin  to  prevent  the  efflorescence  of 

indigo  carmine,  269 
Gmelin,  C.  G.,  memoir  on  the  produc- 
tion of  artificial  ultramarine,  275 


648 


Gmelin's,  process  for  artificial  ultra- 
marine, 278-279 
Goethe,  274 

Gold-button  yellow,  169 
Gold-yellow,  375 
Goulard's  water,  60 
Grape-vine  black,  515 
Grass-green,  185,  554-556 
Gray,  pearl,  185 

slate,  185 
Grays,  575 

Grecian  or  Tyrian  purple,  25 

Green  and  yellow  lake  from  chlorophyl, 

422 

apple  color,  550 

ashes,  548 

blue,  345 

Bremen,  538-543 

bronze,  185,  603 

Brunswick,  543 

chrome,  561-563 

cinnabar,  386,  551,  553 

cinnabar  from  Paris  green,  246 

cobalt,  556-561 

coloring  matter  of  leaves,  421-422 

colors,  532-573 

dark  English,  394 

deep  color,  51 

distilled,  573 

earth,  169,  394 

Eisner,  553 

emerald,  563-568 

English,  550 

Erlaa,  549 

from  chromate  of  zinc,  388 
from  mineral  turbith,  406 
grass,  185 
Hungary,  534 
iris,  534 
Kirchberger,  541 
lake,  544,  554-556 
mineral,  556 

of  naturally  green  coloring 
substance,  555 
leaf,  246,  551 

preparation  of,  50 
light  leaf,  51 
mineral,  549 
Milori,  169,  394,  551 
Mittis,  547 
mountain,  534 
Neuwied,  550 
ochre,  571 

of  stannate  of  copper,  552 
olive,  52,  185 
Pannetier,  563 
Paul  Veronese,  550 
pickle,  55] 
picric  acid;  537 
Prussian,  552 


Green — 

Rinmann,  556-561 
sap,  534-537 
Scheele's,  51 
Schweinfurt,  545-547 
silk,  551 
silky,  387 
titanium,  568-571 
ultramarine,  281,  571-572 
ultramarine,  manufacture  of,  305- 
318 

ultramarine,  transformation  of  into 

blue,  322 
verditer,  538-543 
Verona  earth,  532 
Vienna,  547 
■water,  185 
■without  arsenic,  548 
zinc,  556-561 
Greens,  chrome,  by  mixtures,  386,  387 
compound  of    mineral   blue  and 

vegetable  yellow,  554 
compound  of  vegetable  blue  and 

mineral  yellow,  554 
compound  of  vegetable  yellows  and 

blues,  555 
dark,  575 
English,  169 

from  cadmium  yellow,  401 

from  chloride  of  zinc,  395 

from  Prussian  blue,  203 

in  baths  of  Titus,  copper  com- 
pounds, 31 

magnificent  from  chrome  yellows, 
378 

of  carmine,  indigo,  and  chrome 

yellows,  554 
of  the  Aldobrandini  wedding,  32 
of  the  ancients,  30 
resembling  Scheele's  green,  575 
various  binary  mineral,  552 
with  copper  salts,  549 
yellowish,  575 
Grelley  process  for  cochineal  carmine, 
492 

Grinding  colors,  English  mill  for,  626 
colors,  mill  for,  604,  607 
white  lead  in  oil,  Mr.  Bessemer's 

apparatus,  152 
white  lead  in  water,  150 
Griineberg's   process   for  white  lead, 
97-105 

Guignet,  Mr.,  process  for  emerald  green, 

564 

Guimet,  Mr.,  on  the  preparation  of 
Naples  yellow,  398 

process  for  comparing  ultrama- 
rines, 329-330 

production  of  artificial  ultramarine 
by,  274 


INDEX. 


649 


Guimet — 

process  for  artificial  ultramarine, 
277 

Guynemer,  powdered  dryer  of,  579 
Guyton  de  Morvenu  on  invention  of 
zinc  white,  165 
memoir  of,  on  the  subject  of  zinc 

white,  164 
on  the  composition  of  lazulite,  273 
Gypsum,  55 


HABICH,  G.  C,  on  the  lakes  of  red 
woods,  478-482 
on  the  preparation  of  Paris  blue, 
246 

J.  C,  process  for  the  manufacture 

of  Bremen  blue,  538 
Mr.,  on  the  manufacture  of  neutral 

chrome  yellow,  379 
process  for  artificial  ultramarine, 

301-304 
Hsematoxylin,  484 

Hagen,  R.  de,  improvements  in  sap- 
green,  534-537 

Hallet  and  Stenhouse,  antimony  white 
of,  164 

Hallett  and  Stenhouse's  colors  with  an- 

timonial  basis,  401 
Hamburg  white,  composition  of,  132 

use  of  baryta  in,  193 
Healthfulness  of  Schuzenbach's  process 

for  white  lead,  111 
Heavy-spar,  192-199 
Heeren,  F.,  on  Pattinson's  white  lead, 

90-92 

Heller  on  iodide  of  mercury,  439 

Hepatite,  192-199 

Hermann's  mill,  629 

Hick,  A.,  on  the  preparation  of  Naples 
yellow,  399 

Hcefflmayer  and  Priickner  on  the  pro- 
portions of  materials  for  ferrocyanide 
of  potassium,  231 

Holland  process,  55,  63-78,  98,  101, 
146 

process,  Mr.  Pelouze  on,  73 
white,  composition  of,  132 
white  lead,  composition  of,  134- 
137 

Hopper  white,  183,  184 
Horizontal  tubular  furnace,  178 
Horn,  ferrocyanide  of  potassium  ob- 
tained with,  224-225 
Hues  and  tones,  43-45,  394 
Hues  of  chrome  red,  385 
Hungary  green,  534 
Hydrated  sulphide  of  antimony,  393 
Hydrochloric  acid,  90 

loss  and  economy  of,  194 


Hydrosulphuric  acid,  90 

Hygiene  in  the  manufacture  of  white 

lead,  137-157 
Hygienic   p'recautions   in   white  lead 

works,  72 
Hyposulphate  of  lime,  447 


IMPROVEMENTS  in  the  manufacture 
of  oils,  varnishes,  and  colors,  608- 
629 

Impurities  in  white  lead,  127-134 

India  ink,  531-532 

Indian  blue  of  the  ancients,  29 

red,  486-487 

yellow,  394,  417,  420 
Indigo,  264-267 

adulterations  of,  267 

carmine,  268-269 

composition  of,  266,  267 

mill  for  dry,  607-608 

platt  of,  268 

purple,  268 
Inks,  528 

Institute  of  France,  report  on  zinc 

white,  in  1808,  165 
Iodide  of  lead,  410-411 

of  mercury,  439 
Iris  green,  534 

Iron,  efiFect  of,  upon  yellow  from  weld, 
370 

in  ultramarine,  299 

minium,  425,  501,  504 
analyses  of,  502 
and  coal  tar,  for  wood,  504 
and  red  lead,  comparison  of, 
503 

and  red  ochre,  difference,  426 
composition  of,  425 
employment  of,  503-504 
for  painting  boilers,  504 

the  hulls  of  ships,  504 
mastic  of,  504 
oxide  of,  423 

removing  from  solutions  of  sul- 
phate of  copper,  547 
sesquioxide  of,  424 
use  of  colcothar  on,  503 
violet-brown,  423 
Italian  earth,  361 
raw,  358 
Ivory  black,  530 


JACQUELIN  process  for  preparing  ver- 
milion, 433-434 
Jaune  Indien,  417-420 
Jonquil  chrome  yellow  of  Winterfeld, 

376-377 

yellow  from  chrome  yellows,  877 


650 


INDEX. 


KAOLIN,  306 
for  artificial  ultramarine,  283 
Karmrodt  furnace,  220-222 

process  for  ferrocyanide  of  potas- 
sium, 219-226 
Kassler  yellow,  403 
Ketzinsky,  on  preparing  colors,  49 
Khittel  process  for  madder  lake,  463- 
467 

Kirchberger  green,  547 
Kirchoff  processfor  preparing  vermilion, 
432 

Koechlin,  Camille,  443 

Kopp,  M.  E  ,  memoir  on  the  prepara- 
tion of  the  sulphide  of  antimony, 
445-453 

process  for  madder  lake,  469-471 
Kremnitz  process,  59-63 
Krems  or  Kremnitz  whites,  55,  56,  59- 

63 

white,  analyses  of,  76,  77 
composition  of,  132 
Kuhlmann,  F.,  of  Lille,  on  blanc  fixe, 
193 

on  blue  from  manganate  of  lime, 
262-264 


LAKE,  cochineal,  24,  491 
mineral,  395-396 
of  garanceux,  467-468 
zumatic,  587 
Lakes,  black,  474 
Campeachy,  473 
gr^n,  554-556 

and  yellow  from  chlorophyl, 
422 

of  Brazil  wood,  472 

of   quercitron  and   yellow  wood, 

371-372 
pf  red  woods,  477-483 
Paris,  carmine,  and  Vienna,  493 
testing,  471 
violet,  473-474 

chocolate,  and  red,  475-476 
Lallu  &  Delaunay,  manufacture  of  white 

lead  by,  157 
Larapadius'  pigment  of  red  sulphide  of 

antimony,  441 
Lampblack,  517-524 
Languedoc,  French  man-of-war  painted 

with  zinc  white  in  1786,  165 
Lapis  lazuli,  270 
Laubgrun,  246 
Laundry  blue,  353 

Lavalleye,  P.  T.,  process  for  manufac- 
ture of  a  bituminous  coal  black,  513, 
514 

Lazulite,  270 

analysis  of,  272-278 


Lazulite — 

Guyton-Morveau  on  the  composi- 
tion of,  273 

Margraff  on  the  composition  of, 
273 

Varrentrapp,on  the  composition  of, 
273 

Lead,  absorption  of  carbonic  acid  by,  93 
acetate  of,  158 
antimoniate  of,  161 
antimonite  of,  160 
arsenite  of,  409 
basic  chromate  of,  375-376 
basis,  whites  with,  55,  158 
brown  of  manganate  of,  506 
carbonate  of,  85,  110 
iodide  of,  410,  411 
neutral  chromate  of,  373,  375 
nitrate  of,  86 
oxide  of,  403 
picking  up,  149 
protochloride  of,  403 
white  of  basic  chloride  of,  158-159 

of  sulphate  of,  159 

tungstate  of,  159-160 
Leaf  green,  246,  551 

preparation  of,  50 
red,  484 

Leaves,  green  coloring  matter  of,  421- 
422 

Leclaire,  M.,  manufacture  of  zinc  white 
by,  166,  180 
use  of  peroxide  of  manganese  for 
quick  drying  of  zinc  white,  187- 
188 

Lef^vre,  Th.,  apparatus  for  pulveriz-  ' 
ing  white  lead,  140-145 
production  of  the  white-lead  works 
of,  146 

white  lead,  works  of,  145-153 
Lefort,  J.,  on  dryers,  188-189 

on  the  manufacture  of  aurum  mus- 

sivum,  421 
on  the  use  of  oxide  of  manganese 

by  the  Romans,  505 
process  for  madder  lake,  462 
process  for  manufacture  of  manga- 
nese brown,  505-506 
Lemnos  earth,  425 
Lemon  color,  185 
yellow,  169,  395 

chromate  of  baryta,  379 
Lengths,  measures  of,  633 
Lenzinite,  334 

Le  Play  on  manufacture  of  white  lead 

in  England,  69,  72 
Lichens,  archil,  Stenhouse's  researches 
on,  496-497 
liquors  from,  497 
precipitates  from,  f497 


INDEX. 


651 


Liebig,  Baron,  process  for  manufacture 
of  a  dense  neu- 
tral chromate 
of  lead,  374 
of  Schweinfurt 
green,  645 
Ligbt  English  green,  169,  394 
leaf  green,  51 
white,  or  silver  white,  127 
Lille,  manufacture  of  white  lead  at  66, 

71,  73,  74 
Lime  blue,  341-351 

of  manganate  of,  262-264 
carbonate  of^  53-54 
chromate  of,  378 
hyposulphite  of,  447 
in  ultramarine,  299 
metallic,  455 

tartrate  of,  painting  with,  165 

white  with  basis,  53-54 
Limekilns,  vitreous  substance  produced 

in,  in  Palermo,  274 
Linseed  oil,  action  of  white  lead  on,  58 
Litharge,  56,  115,  409,  410 

commercial,  103 

for  gilt  brown,  507 

in   Griineberg's  process  for  white 
lead,  103 

preparation  of,  in  England,  84 
Litmus,  356 

London  Journal  of  Arts,  231 
Loppens,  Mr.,  on  iron  minium,  502 
Louyet,  Mr.,  on  Rinmann  green,  558 
Louyet's  process  for  ascertaining  the 

impurities  in  white  lead,  129-132 
Ludwig,  Mr.,  on  smalt,  351 
Lump  white  lead,  powdering,  151-152 
Luteolamide,  371 
Luteolin,  368,  370,  371 

analysis  and  chemical  formula  of, 

370-371 
red  substance  from,  371 
violet  substance  from,  371 


MACHINE  of  J.  Poelmann  for  separat- 
ing white  lead  from  the  metal, 
154-155 

Ward,    for   the    manufacture  of 
white  lead,  138-140 
Madder  carmine,  473,  477 

detection  of  adulterations  of,  458, 
460 

lake,  458-475 

lakes,  uses  of,  471 

various  colors  of,  468,  471 

sulphuric  charcoal  of,  463 
Magdeburg  white  lead,  analysis  of,  76 
Malachite,  534 

Manganate  of  lead,  brown  of,  506 


Manganate — 

of  lime,  blue  of,  262-264 
Manganese,  benzoate  of,  583 

borate  of,^  585 

brown,  505-506 

ores,  use  of,  by  the  ancients,  19 
peroxide  of,  as  a  dryer  of  zinc  white, 
187-189 

Margraff  on  the  composition  of  lazulite, 
273 

Marie  Louise  blue,  51 

Maroon  red,  440 

Mars  browns,  423,  500,  501 

reds,  423 

violets,  423 

yellow,  358,  362-364 
Massicot,  58,  115,  358,  409-410 
Mastic  of  iron  minium,  504 

zinc  white  in,  168 
Mathieu,  M.,  memoir  on  the  oxide  of 

zinc,  1844,  166 
Mathieu-Plessy,   Mr.,  on  vermilion  of 

antimony,  441-445 
Measures,  American,  635 

Btitish  imperial,  635 

of  capacity,  634 

of  length,  633 

superficial,  634 
Mercury,  chromates  of,  439-440 

iodide  of,  439 

red  sulphide  of,  430 
Merimee,  17,  18,  30 

on  artificial  ultramarine,  277 

on  the  effect  of  the  addition  of 
alumina  to  chromates,  376 

on  the  preparation  of  mineral  yel- 
low, 404 
Metallic  lime,  455 

Metals,  bronze  compositions  for,  595- 
599 

Metric  system,  631 

of  weights  and  measures,  631- 
640 

Meudon  white  in  white  lead,  128 
Mill,  English,  for  grinding,  626 
for  dry  indigo,  607-608 
for  grinding  colors,  604-607 
Hermanns,  629 
Millon,  Mr^,  on  chromates  of  mercury, 
439 

Milori  green,  169,  394,  551 
Mineral  blacks,  512-514 

blue,  256-257 

gamboge,  358 

green,  549 
lake,  556 

lake,  395-396 

straw-yellow,  406 

turbith,  406 

yellow,  358,  394,  403,  404,  405 


652 


Mineral,  yellow — 

superfine,  405 

Miniature  painting,  ultramarine  for,  282 

Minium,  426-428 

iron,  425,  501-504 
analyses  of,  502 
employment  of,  503-504 

Mittis  green,  547 

Mixed  or  compound  colors,  393-395 

Mixeological  principle,  the,  50-52 

Mixing  of  colors,  394 

Mixture  of  colors,  37 

Mock  gold,  420-421 

Modification  of  contrast,  47 

Mollerat,  manufacture  of  zinc  white  by, 

in  1808,  165 
Montabert,  M.,  on  the  use  of  antimony 

white,  162-164 
Monthier's  blue,  253 
Montpellier  yellow,  403 
Morea  berries,  366 
Mosaic  gold,  420-421 
Mountain  blue,  341-351 

~  green,  534 
Muffles,  French,  321-322 
Mulder,  M.,  analyses  of  white  leads,  76, 
77 

on  composition  of  samples  of  white 
lead,  134-137 

on  Holland  white  lead,  76 

on  orange  mineral,  428 
Mulhouse  white  lead,  126 
Mullin's  apparatus,  106-110 

patent,  105 

process  for  white  lead,  105-110 
Murdock's  process  for  fabrication  of 

oxide  of  zinc,  180-182 
Murex,  Tyrian  purple  extracted  from, 

26 


ANKIN  yellow,  421 

Naples  yellow,  358,  394,  399-400 
Natural  sulphate  of  baryta,  192 
Neutral  chromate  of  lead,  373-375 
Neuwied  green,  550 

Newton,  W.  E.,  process  for  vegetable 

blacks,  525-526 
Nitrate  of  copper,  342 
Nitrate  of  lead,  86 

basic  for  production  of  carbon- 
ate of  lead,  115 
Nitrogen  utilized,  224,  225 
Normal  colors,  37 


OCHRE,  auri  pigraentum  of  the  an- 
cients, 20 
Burgundy,  as  a  substitute  for  red 
lead,  501 


Ochre — 

from  la  Berjaterie,  359 

from  St.  George-sur-la-Pree,  359 

green,  571 

of  Athens,  20 

rut,  361 
Ochres,  358-361 

natural,  preparation  of,  362 

red,  360,  423-424 

used  by  the  ancients,  19 
Ochreous  clay,  425 
Oil,  drying  without  lead,  168 

drying  with  peroxide  of  manganese, 
168 

or  lampblack  process,  521-524 
paints,  spreading,  drying,  and  ad- 
hering properties  of,  588-593 
Oils,  drying,  578 

varnishes  and  colors,  Bessemer  & 
Heywood's  improvements  in  the 
manufacture  of,  608-629 
Olive  green,  52,  185 
Operating  the  apparatus  for  oxide  of 
zinc,  177 
for  gilt-brown,  507 
Orange  mineral,  428-429 
paste,  375 

red   sulphite  of  antimony,  392- 

393 

Orchil,  474 
Orcin,  495 

Ordinary  process  for  cochineal  carmine, 
490 

Oriental  bole,  425 

brown,  comparison  of  iron  minium 
with,  503 
Origin  of  colors,  37-39 
Orpiment,  358,  407-408 
Orpin  or  orpiment,  358,  407-408 
Ostrum  of  the  Romans,  25 
Oxide  of  antimony,  161 

of  copper,  blue  colors  from,  345 

of  iron,  423 

of  lead,  preparation  of,  112 

preparation  at  Portillon,  80 
treatment  of,  by  Mullin's  pro- 
cess, 108 
of  zinc,  162 

compound  colors  with,  395 
fabrication  of,  by  the  Mur- 
doch process,  180-182 
M.  Mathieu's  memoir  on,  in 

1844,  166 
process  from  The  Technolo- 
giste,  169-180 
Oxidizing  metals,  mode  of,  108 

room  for  zinc,  171 
Ozouf,  G.  H.,  safe  apparatus  for  the 
preparation  of  white  lead,  154 


INDEX. 


653 


PACKING  white  lead,  153 
Painted   papers,  blue   ashes  for, 
342 

Painter's  bronze,  420-421 
Pale  ultramarines,  298 

yellow,  169,  395 
Pannetier  green,  563 
Paper  hangings,  chromate  of  baryta 
for,  379 
use  of  weld  lake  for,  370 
Papers,  painted,  blue  ashes  for,  342 
smooth,  use  of  zinc  white  in  the 
manufacture  of,  168 
Paris  blue,  244-253 
lake,  493 

Passalaqua,  colors  employed  in  the 
Egyptian  collection  of,  21 

Patera,  Mr.,  process  for  the  manufac- 
ture of  uranium  yellow,  411 

Pattinson  process,  85-92 

Pattinsoii's  white  lead,  observations  on, 
90-92 

Paul  Veronese  green,  550 
Peach-stone  black,  515 
Pearl-gray,  185 
Pech-urane,  411 
Peligot  blue,  261 

Pelletier  on  the  preparation  of  blue 

ashes,  341 
Pelouze  and  Fremy  on  brightening  the 

color  of  vermilion,  437 
Pelouze,  Mr.,  on  Holland  process,  73 
Perchloride  of  chromium,  499-500 

of  tin,  481-482 
Perkin,  W,  H.,  process  for  black  from 

sulphate  of  aniline,  524 
Peroxide  of  manganese  as  a  dryer  for 

zinc  white,  187-189 
Persian  berries,  366 

coloring  matter  of,  368 
Persoz  process  for  madder  lake,  461 
Phyllocyanin,  422 
Phylloxanthin,  422 
Physical  effects  of  colors,  46-48 
Picking  up  lead,  149 
Picric  acid,  green,  537 
Pigments  with  zinc  for  basis,  169 
Pink  and  red  lakes,  471-473 

cobalt,  454 
Pinks,  575 

and  reds  of  madder  lake,  463 
dark,  575 
madder,  471 
Piatt  of  indigo,  268 
Pliny,  17,  18,  19,  20,  23,  26 
Poelmann,  J.,  machine  for  separating 

white  lead  from  the  metal,  154-155 
Pohl,  J.  J.,  269 

Pompeii,  blues  discovered  at,  by  Sir  H. 
Davy,  29 


Pompeii — 

Chaptal's  examination  of  the  paints 

found  at,  32 
ochres  used  in  paintings  in,  21 
Porcelain  clay,  306 

use  of  purple  of  Cassius  for  paint- 
ing, 458 
Potash,  Russian,  224 
Potassa,  bichromate  of,  388 
chromate  of,  388 
chromates  of,  373 
yellow  chromate  of,  for  green  cin- 
nabar, 553 
Potassium,  ferrocyanide   of,  manufac- 
ture of,  205-219 
Portillon,  grinding  white  lead  in  oil  at,83 
manufacture  of  orange  mineral  at, 
429 

manufacture  of  red  lead  at,  427 
manufacture  of  white  lead  at,  79-84 
manufacture  of  zinc  white  at,  182 
Portuguese  red,  484 
Powder,  face,  zinc-white,  in  manufac- 
ture of,  168 
Powdered  dryer  of  Guynemer,  579 
Powdering  lump  white  lead,  151-152 
Pozzouli,  blue  made  at,  30 
Precautions  to  render  manufacture  of 

white  lead  less  unhealthy,  155-157 
Preparing  colors,  general  method  of, 
49-52 

Prickle-wood  black,  515 
Primary  colors,  37,  46,  48 
Printing  power  of  ultramarine,  trial  of, 
336 

ultramarine  for,  282 
Prismatic  spectrum,  37 
Production  of  the  white  lead  works  of 

Mr.  Lefevre,  146 
Protochloride  of  manganese,  505 

of  tin,  481 
Priickner,  C.  P.,  on  comparing  ultra- 
marines, 331-333 
process  for  artificial  ultramarine, 
283-288,  300 
Prussian  black,  531 
blue,  199-244,  474 

and  ammonia,  253 
application  of,  203 
by  Brunnquell  process,  205- 
219 

by  the  Stephens  process,  235- 
239 

calcination  of,  243 
composition  of,  199 
discovery  of,  199 
effect  of  damp  walls  on,  203 
effect  of  the  alkalies  on,  202 
English  process  of  manufac- 
ture, 239-244 


654 


INDEX. 


Prussian  blue — 

for  dyeing,  printing,  and  writ- 
ing, 235,  237,  238 

green  lakes  from,  554 

greens  from,  202 

intensity  of,  203 

Karmrodt  process,  219-226 

manufacture  of  ordinary,  200 

preservation  of  the  color  of,  by 
acid  sulphate  of  potassa, 
242 

process  for  rendering  soluble, 

235,  237 
pure,  200 

reducing  the  expense  of  manu- 
facture, 242 

testing  the  value  of,  and  its 
adulterations,  254-256 

to  judge  of  the  beauty  of,  203 

tones  of,  202 

variation  in  the  intensity  of, 
200 

velvety  blacks  from,  203 
brown,  506 
green,  552 
Puce  color,  with  chromate  of  manga- 
nese, 512 

Pulverizing  white  lead,  Lefevre's  ap- 
paratus for,  140,  145 
ordinary  process  of,  141 
Pure  or  broken  colors,  39 
Purity  of  white  leads,  testing,  127-134 
Purple,  indigo,  268 
madder  lake,  463 
of  Cassius,  455-458 
-red,  440 


QUERCITRON  and  yellow  wood,  lakes 
of,  371-372 
bark,  yellow  from,  358 


RAYS  of  the  solar  spectrum,  colors 
of,  46 

reflected  by  colors,  37 

reunion  of,  46 
Raw  sienna,  511-512 
Realgar,  429 

Red  and  pink  lakes,  471-473 
and  violets  from  archil,  495 
Antwerp,  362 
hole,  425 
-brown,  426,  507 
colors,  423-500 
chrome,  382,  385-387,  500 

hues  of,  385 
employed  by  the  Greeks  and  Ro- 
mans, 21 
English,  424 


Red- 
Indian,  486-487 
in  plates,  484 
lake,  475-476 
lead,  426-428 

known    to    the   Greeks  and 
Romans,  23 

substitute  for,  501 
leaf,  484 
maroon,  440 
ochre,  360,  423,  424 
Portuguese,  484 
Prof.  Dussauce  on  a  new,  486 
purple,  440 

sesquioxide  of  iron,  424 
Spanish,  484 

substance  obtained  from  luteolin, 
371 

vegetable,  484 
Venice,  362 

woods,  lakes  of,  477-483 
Reds,  madder,  471 
Mars,  423 

used  by  the  Egyptians,  21 
Resin  lampblack,  518 
Resins  for  dryers,  584 
Retin,  asphaltum,  509 
Retorts  for  zinc,  173,  175,  177 
Reverberatory  furnace  or  coke  oven,  178 
Rhamnin,  368 
Rhamnoxanthin,  475-476 
Ringault,  Mr.,  patent  for  vermilion  un- 
alterable by  fire,  438 
Rinmann  green,  556-561 
analysis  of,  560 
prepared  by  Barruel  and  Lec- 

laire,  560 
R.  Wagner  on,  557-560 
Ritter,  H.,  on  composition  of  artificial 
ultramarine,  327 
on  the  manufacture  of  Holland  ver- 
milion, 430 
Robiquet  and  Colin  process  for  madder 
lake,  460 
discovery  of  orcin  by,  495 
Robiquet's  formula  for  artificial  ultra- 
marine, 296 
Romans  and  Egyptians,  white  used  by, 
17 

Roman  yellow,  394,  574 

Rostaing,  Mr.  de,  361 

process  for  white  lead,  126 

Rousseau,   Bobierre,  and  Ruolz,  anti- 
mony, white  of,  161-162 

Royal  yellow,  408 

Rubia  tinctorum,  458 

Ruby  of  arsenic,  429 

Ruolz,  Bobierre,  and  Rousseau,  anti- 
mony white  of,  161-162 

Rut  ochre,  358,  361 


INDEX. 


655 


SACC  process  for  madder  lake,  469 
Saffron  yellow,  358 
Saint  Cyr  white,  184 
Sal  ammoniac  and  ultramarine,  323 
Salvetat,  Mr  ,  process  for  brown,  500 
Sandaraca  of  the  Romans,  20 
Santaline,  472 
Sap  green,  534-537,  555 
Saxony  blue,  268,  351 

smalts  of,  marks  of,  353 
Scarlet,  iodide  of  mercury,  439 
Scheele's  green,  51,  543,  545 

green,  green  resembling,  575 
Sching  C,  process  for  manufacture  of 

ferrocyanide  of  potassium,  226-230 
Schist,  512-513 

Schuzenbach's  process  for  white  lead, 

110-111 
Schweinfurt  green,  545-547 
Scoffern,  Mr.,  159 
Secondary  colors,  37 
Seine,  manufacture  of  white  lead  in 

Department  of,  67,  70 
Separation  of  oxide  of  zinc  from  metal- 
lic zinc,  183 
white  lead   from   the  uncor- 
corroded  metal,  149 
Sepia,  510-511 
Sesquioxide  of  iron,  424 
Sewell's  apparatus  for  white  lead,  113- 
114 

process  for  white  lead,  111-115 
Shale  black,  512-513 
Ships,  hulls  of,  painting,  504 
Sienna  earth,  361,  511,  512 
raw,  358 

Silica  for  artificial  ultramarine,  290 
Siliceous  sand,  analysis  of,  290 
Silk  green,  551 
Silky  green,  387 
Silver,  chromate  of,  440 

white,  or  light  white,  127 
Sky  blue,  253 

English,  356-357 
Slate-gray,  185 
Smalt,  351-354 

blue,  351 

color  of,  351 

of  a  magnificent  blue,  353 
raw  materials  of,  351 
Smalts  of  Saxony,  marks  of,  353 
Snow  white,  182 
Society  d'Encouragement,  137 
Soda,  carbonate   of,  for  ultramarine 
green,  308 
furnace,  blue  substance  produced 

in,  274 
in  ultramarine,  299 
sulphate  of,  for  ultramarine  green, 
307 


Sodium,  309 

Solar  spectrum,  color  of  rays  of,  46 
Sorel,  Mr.,  process  for  separating  oxide 

of  zinc  from  metallic  zinc,  183 
Spanish  red,  484 

white,  54 
Spilsburg,  Mr.,  160 
Spindle  tree  black,  515 
Stannate  of  protoxide  of  gold,  457 
Stardi  blue,  351 

Stein,  v.,  on  manufacture  of  picric  acid 

green,  537 
Stenhouse  and  Hallett,  antimony  white 

of,  164 

Stenhouse,  Mr.,  analysis  of  Indian  yel- 
low, 418 

Stephens'  process  for   preparation  of 

Prussian  blue,  235 
Stil  de  grain,  358,  366,  368 

preparation  of,  366-367 
Stinking  stone,  192 
Stone  color,  185 
Straw-yellow,  185 

from  chrome-yellows,  377 
mineral,  406 
Struve,  C,  analysis  of  green  without 

arsenic,  548 
Subphosphate  of  cobalt,  257 
Sulphate,  atomic,  190-191 
of  baryta,  192-199 

in  white  lead,  132-133 
of  iron,  224 

of  soda  for  ultramarine  green,  307 
of  zinc,  colors  for,  574-577 
Sulphide  of  antimony,  441 

analysis  of,  444-445 
compound  colors  with,  393 
orange  red,  392,  393 
of  sodium  for  ultramarine,  309 
of  zinc,  191-192 
Sulphite  of  lead,  white  of,  159 
Sulpho-antimonite  of  barium,  453-454 
Sulphoindigotic  acid,  268 
Sulphur,  309 

combination  with  ultramarine,  323 
for  artificial  ultramarine,  291 
transformation  of,  into  hydrosul- 
phuinc  acid,  90 
Sumach  lake,  475 
Superficial  measures,  634 
Symbols  for  abbreviations,  637 

TABLES  of  French  and  English  weights 
and  measures,  633-640 
Tar  black,  518-521 
Tartrate  of  lime,  painting  with,  165 
Technologiste,  154,  163,  169,  205,  231, 
259,  283,  289,  301,  305,  328,  345, 
379,  399,  418,  463,  486, 534,  538,  551, 
557,  566. 


656 


INDEX. 


Terra-merita,  358,  364-365 
Terra-rosa,  312 
Tertiary  colors,  49 
Tessart,  274 

Testing  madder  lakes,  471 

Prussian  blue,  232,  254-256 

the  purity  of  white  leads,  127-134 
Thenard  blue,  257-261 

Mr,,  process  for  white  lead,  78-85 

on  process  for  separating  ultra- 
marine from  lazulite,  270 

on  the  preparation  of  Naples  yel- 
low, 397 
Theophrastes,  17,  23,  32 
Thierry-Mieg  and  Schwartz  process  for 

lake  of  garenceux,  467-468 
Tin,  480 

basic  chromate  of,  395 

bath,  dyers,  459 

bisulphide  of,  420 

perchloride  of,  481,  482 

protochloride  of,  481 

white,  165 
Tint  of  azure  blue,  185 
Tiremon  process  for  artificial  ultrama- 
rine, 280 

Tiremon' s  formula  for  artificial  ultra- 
marine, 277 

Titanium  green,  568-571 

Titrated  liquor,  preparation  of,  234 

Tone,  contrast  of,  46 

Tones  and  hues,  394 

Tubular  furnace,  horizontal,  178 

Tuckert,  Mr.,  on  the  manufacture  of 
Holland  vermilion,  430 

Tungstate  of  lead,  white  of,  159-160 

Turbith  mineral,  406 

Turnbull's  blue,  244 

Turner  yellow,  358,  403 

Turkey  berries,  366 

Tyrian  purple,  25 

Tyrolese  white  lead,  193 


ULMIN  blacks,  525 
brown,  507-508 
Ultramarine,  analysis  of,  272 
and  sal  ammoniac,  323 
artificial,  274-340 

analysis  of,  275,  296-297 
Brunner's  process,  289-300 
Dippel  process,  300-301 
Geutele  processes,  304-323 
Gmelin's  formula  for,  276 
Gmelin's  process,  278-279 
Guimet's  process,  277-278 
Habich  process,  301-304 
Pruckner  process,  283-288, 
■  800 

Robiquet's  formula  for,  276 


Ultramarine,  artificial — 

Tiremon's  formula  for,  277 
Tiremon  process,  280 
Weger  process,  281-282 
Winterfield  process,  288-289 
ash,  270 

blue,  fine  green  for,  316 

Gentele's  process,  318-323 
real  or  native,  270 
***  separation  from  lazulite,  270 

washing,  322 

blues,  269-340 

cobalt,  340 

combined  with  sulphur,  323 
dark  alum,  composition  for,  324 
durability  of  color  of,  333 
for  calico  printing,  330 
for  miniature  painting,  282 
for  printing,  282 
Fiirstman  process  for,  323-327 
green,  281,  571,  572 

manufacture  of,  305-318 
proportions  of  raw  materials, 

310-311,  316-318 
raw  materials  for,  305 
lazulite,  270 

method  of  ascertaining  the  quality, 
288 

mixture  for,  291 

resistance  to  the  action  of  alum, 

333 

trial  for  the  proportion  of  size,  337 
of  coloring  power  of,  334 
of  the  glazing  power  of,  337 
of  the  printing  power  of,  336 

white,  327 

yellow,  379 
Ultramarines,  composition  of,  339-340 

pale,  298 

trial  and  analysis  of,  329-339 
Ultramarinometer,  335-336 
Umber,  511 

Uranium  pech-blende,  411 

yellow,  411,  416 
Ure,  Dr.,  57 


VALLE    and    Barreswill,  antimony 
white  of,  162-164 
Value  of  fused  materials  in  the  manu- 
facture of  ferrocyanide  of  potassium, 
280-235 
Van  Dyke  brown,  504-505 
Varnishes,  oils,  and  colors,  Bessemer 
and  Heywood's  improvements  in  the 
manufacture  of,  608-629 
Varrentrapp   on   the   composition  of 

lazulite,  273 
Vauquelin,  17,  27,  274 

discovery  of  chromium  by,  372 


INDEX. 


657 


Vegetable  blacks,  515 

green,  554-556 

red,  484 

violet,  484 
Venice  lake,  472,  478 

red,  362 

white,  composition  of,  132 

white,  use  of  baryta  in,  193 
Verdet,  crystallized,  573 
Verdigris,  394,  572 

use  of,  by  the  ancients,  32 
Verditer  blue  aud  green,  538-543 

in  paste,  345 
Vermilion,  430-439 

Brunuer  process,  432,  433 

by  the  dry  way,  430 

by  the  wet  way,  49,  431 

Chinese  method  of  preparing,  431 

discovery  of,  in  Rome,  23 

Firmenich  process,  434-437 

Holland,  manufacture  of,  430 

Jacquelin  process,  433-434 

Kirchoff  process,  432 

of  antimony,  441 

preparation  of,  448 
properties  of,  452-453 

processes  for  brightening  the  color 
of,  437 

unalterable  by  fire,  438 
Vernet,  Horace,  278 
Verona  earth,  green,  532 

use  of,  by  the  Romans,  31 

yellow,  403 
Versepuy's  apparatus  for  white  lead, 
95-96 

process,  93-97 
Vienna  green,  547 

lake  493 
Violet  lakes,  473-474,  475-476 

from  iron,  423 

solution  obtained  from  luteolin, 
371 

Violets,  vegetable,  484 

Mars,  423 
Vitreous  substance  from  lime-kilns,  pro- 
duced in  Palermo,  274 
Vitruvius,  17,  18,  20,  21,  23,  25,  27,  31 
Vitry  white,  184 

Vlaandern,  experiments  on  composition 
of  white  lead,  134-137 


WAGNER,  R.,  analysis  of  chromate  of 
zinc,  391 
on  economy  of  iron  minium,  426 
on  Rinmann  green,  557-560 
on  sulpho-antimonite  of  barium, 
453 

on  the  preparation  of  yellow  orpi- 
ment,  408 

42 


Wagner,  R. — 

process  for  the  preparation  of  In- 
dian yellow,  418 
Ward  machine  for  the  manufacture  of 

white  lead,  138-140 
Warington,  R.,  on  the  preparation  of 

Paris  blue,  245 
Washer,  Crompton's,  117 
Water-green,  185 

Watin's  process  for  distinguishing  white 

lead  fi'om  chalk,  128 
Weger  process  for  artificial  ultramarine, 

281-282 
Weights,  635 

and  measures,  metric  system  of, 
631-610 

Weilhem,  Mr.,  on  the  preparation  of 

Erlaa  green,  549 
Weld  lake,  368-371 
yellow  from,  369 
yellows,  358 
Weshle,  Mr.,  on  the  preparation  of  ver- 
milion, 433 
Wet  way,  advantages  of,  in  preparing 
colors,  49 

White  and  gray  pigments  of  oxide  of 
zinc,  168 
azure,  185,  203 
colors,  53-199 

of  basic  chloride  of  lead,  158-159 
*     of  sulphate  of  lime,  55 
of  sulphite  of  lead,  159 
of  tungstate  of  lead,  159-160 
Saiut-Cyr,  184 
snow,  zinc,  hopper,  183 
tin,  165 

ultramarine,  327-328 
vitry,  184 

zinc  and  dryers,  186-189 
\Vait3s,  antimony,  161-164 
baryta,  192-199 

employed  in  painting,  natural  or 
chemical  compounds,  37 

used  by  the  Egyptians  and  Romans, 
17 

with  lead  bases,  55-158 
with  lime  bases,  53-54 
zinc,  576 
White  lead,  analyses  of,  76,  77 

analysis  of,  made  by  Wood, 
Benson,  and  Griiueberg,  pro- 
cess, 102 
Bacco's  process  for  testing, 

133-134 
beds  for,  147,  148 
by  Crompton  process,  1 1 5-1 25 
by  Gannal's  process,  125-126 
by  Holland  or  Dutch  process, 
63-78 

by  Kremnitz  process,  59-63 


658 


White  lead- 
by  Mullin's  process,  105-110 
by    Schuzenbach's  process, 

110-111 
by  the  Pattinson  process,  85- 

92 

by  Versepuy  process,  93-97 

chalk  in,  128 

composition  of,  134-137 
'     of  samples  of,  132-137 

deaths  from,  138 

dry  grinding  scales  of,  149 

drying  rooms,  150 

fine,  should  be  free  from  cop- 
per, 104 

French  process,  78-85 

grinding  in  water,  150 

harmlessness  of  the  manufac- 
ture of,  by  Lallu  and  Delau- 
nay,  157 

in  oil,  83 

grinding  of,  at  Portillon, 
83 

in  powder,  82 
keeping,  128 

Leffevre's  apparatus  for  pul- 
verizing. 140,  145 

Lonyet's  process  for  ascertain- 
ing the  impurities  in,  129- 
132 

machine  for  separating  from 

the  metal,  154-155 
Mulhouse,  126 

observations  on  Pattinson's, 

90-92. 
packing,  153 

powdering  lump,  151-152 

precautions  to  render  less  un- 
healthy, 155-157 

processes  for  rendering  manu- 
facture of,  less  unhealthy, 
137-157 

processes  of  Wood,  Benson, 
and  Griineberg,  97-105 

produced  in  the  works  of  M. 
Lefevre,  146 

Rostaing's  process  for,  126 

testing  the  purity  of,  127- 
134 

Tyrolese,  193 

washing  in  carbonate  of  soda, 
115 
tanks  for,  82 
"Woolrich  process,  92-93 
works,   hygienic  precautions 
in,  72 

Wingens,  Mr.,  process  for  Schweinfurt 

green,  546 
Winterfield,  jonquil  chrome  yellow  of, 

376-377 


Winterfield  process  for  artificial  ultra- 
marine, 288-289 

Wohler,  Mr.,  on  perchloride  of  chro- 
mium, 499 

Wood,  Benson,  and  Griineberg  processes 
for  white  lead,  97-105 

Wood  charcoal,  alkalized  charcoal  from, 
224 

painting  with  iron  minium  and  coal 
tar,  504 

process  for  cochineal  carmine,  492 
Wood's  apparatus  for  white  lead,  98 
Woolner,  modification  of  Wood's  pro- 
cess for  white  lead  by,  102 
Wool  process  for  cochineal  carmine,  491 
Woolrich  process,  92-93 
Wuy,  balls  of,  357 


YELLOW,  antimony,  394,  405 
baryta,  169 
bouton  d'or,  169 
bright,  394 
cadmium,  400-401 
cassei,  403 
chamois,  574 

chromate  of  lead,  neutral,  composi- 
tion of,  374 
chromate  of  potash,  373 
chrome,  379-385 
Cologne,  377-378 
colors,  258-422 
from  weld,  extracting,  369 
gold,  375 

hues  of  chrome,  382 
Indian,  394,  417,  420 
jonquil  of  Winterfield,  376-377 
Kessler,  403 
lemon,  169,  395 

lemon  of  chromate  of  baryta,  379 
Mars,  362-364,  394 

calcining  to  produce  browns, 
500 

mineral,  403,  404 

straw,  406 
Montpellier,  403 
Nankin,  421 
Naples,  394,  397-400 

tones  and  hues  of,  from  anti- 
mony, 402 
ochre,  358,  359 

with  glue  size  or  oil,  361 
of  antimony  and  zinc,  401-403 
pale,  169,  395 
protoxide  of  lead,  409 
realgar,  407-408 
Roman,  394 
royal,  408 
straw,  185 

sulphide  of  arsenic,  407-408 


INDEX. 


659 


Yellow- 
tones  of  chrome,  383 

Turner,  403 

ultramarine,  379 

uranium,  411-416 

Verona,  403 

wood,  358 

lakes  of,  371-372 
Yellowish-greens,  575 

sap-green,  537 
Yellows,  chamois,  574 

chrome,  372-387,  394 

dark  gold,  575 

delicate  light,  574 

gold,  575 

in  general,  358 

of  the  Aldobrandini  Wedding,  21 
Roman,  574 

used  by  the  ancients,  20 
zinc,  of  Germany,  391 


ZAFFER,  351 
blue,  351 

Zinc,  acetates,  chlorides,  nitrates,  ox- 
ides, sulphate  of,  576 
and  iron,  brown  from,  501 
as  a  basis  for  pigments  for  artists 

and  house  painters,  169 
basic  chromate  of,  394 
charging  with  the  retorts,  177 
chromate  of,  387-391 

and  oxide  of,  compound  colors 
with,  393 
colors  of  sulphate  of,  574-577 
flowers  of,  181 
furnnces  for,  169-175 
green,  556-566 

of  Barruel  and  Leclaire,  560 


Zinc- 
melting,  171 
ore,  distillation  of,  167, 

operating  with,  177,  178 
oxide  of,  162 

apparatus    for  manufacture 

of,  169-180 
fabrication  by  the  Murdoch 

process,  180-182 
process   from    the  Technolo- 
gists, 169-180 
oxidizing  room  for,  171 
retorts  for,  173,  175,  177 
separation  of  oxide  of,  from  metal- 
lic, 183 
sulphide  of,  191-192 
white,  164,  183,  192,  576 

adulteration  of,  189-190 
and  dryers,  uses  of,  186-189 
danger  and  salubrity  of,  190- 
191 

dryer  for,  578 
in  1770,  164 

invention  of,  claimed  for  France 

in  1781,  165 
manufacture  of  at  Portillon, 

182 

manufacture  of,  by  Mr.  Le- 
claire, 166-180 
mixture  of,  with  pigments,  168 
product  of,  167 
uses  of,  168 

various    pigments  obtained 

from,  184 
various  processes  for  the  man- 
ufacture of,  185-186 
yellows  of  Germany,  391 
Zumatic  dryer,  580 
lake,  587 


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A  Series  of  Rules  and  Tables  for  the  use  of  Engineers,  etc.  By 
Thomas  Box.   12mo   $2.50 

BBOWN.— Five    Hundred    and    Seven  Mechanical 
Movements : 

Embracing  all  those  which  are  most  important  in  Dynamics,  Hydrau- 
lics, Ilydi-ostntics,  Pneumatics,  Steam  Engines,  Mill  and  other  Gear- 
ing, Presses,  Horology,  and  Miscellaneous  Machinery  ;  and  including: 
many  movements  never  before  published,  and  several  of  which  have 
only  recently  come  into  use.  By  Henry  T.  Brown,  Editor  of  the 
"  American  Artisan."    In  one  volume,  12mo.       .      .       .  $1.00 


HENRY  CAREY  BAIRD'S  CATALOGUE.  5 


BUCKMASTEB,.— The  Elements  of  Mechanical  Phy- 
sics : 

By  J.  C.  BuCKMASTER,  late  Student  in  the  Government  School  of 
Mines ;  Certified  Teacher  of  Science  by  the  Department  of  Science 
and  Art ;  Examiner  in  Chemistry  and  Physics  in  the  Royal  College 
of  Preceptors;  and  late  Lecturer  in  Chemistry  and  Physics  of  the 
Royal  Polytechnic  Institute.  Illustrated  with  numerous  engravings. 
In  one  volume,  12mo  $1.50 

BULLOCK.— The  American  Cottage  Builder : 

A  Series  of  Designs,  Plans,  and  Specifications,  from  $200  to  $20,000, 
for  Homes  for  the  People ;  together  with  Warming,  Ventilation, 
Drainage,  Painting,  and  Landscape  Gardening.  By  John  Bullock, 
Architect,  Civil  Engineer,  Mechanician,  and  Editor  of  "  The  Rudi- 
ments of  Architecture  and  Building,'^  etc.,  etc.  Illustrated  by  75  en- 
gravings.   In  one  volume,  8vo  $3.50 

BULLOCK.  — The  Rudiments  of  Architecture  and 
Building : 

For  the  use  of  Architects,  Builders,  Draughtsmen,  Machinists,  Engi- 
neers, and  Mechanics.  Edited  by  John  Bullock,  author  of  "  The 
American  Cottage  Builder."  Illustrated  by  250  engravings.  In  one 
volume,  8vo  $3.50 

BURGH.— Practical  Illustrations  of  Land  and  Marine 
Engines : 

Showing  in  detail  the  Modern  Improvements  of  High  and  Low  Pres- 
sure, Surface  Condensation,  and  Super-heating,  together  with  Land 
and  Marine  Boilers.    By  N.  P.  BuRGH,  Engineer.    Illustrated  by 
■  20  plates,  double  elephant  folio,  with  text .         .       .       .  $21.00 

BURGH.— Practical  Rules  for  the  Proportions  of  Mo- 
dern Engines  and  Boilers  for  Land  and  Marine 
Purposes. 

By  N.  P.  Burgh,  Engineer.   12mo  $1.50 

BURGH.— The  Slide-Valve  Practically  Considei*ed. 

By  N.  P.  Burgh,  Engineer.    Completely  illustrated.    12mo.  $2.00 

BYLES.— Sophisms  of  Free  Trade  and  Popular  Politi- 
cal Economy  Examined. 

By  a  Barrister  (Sir  John  Barnard  Byles,  Judge  of  Common 
Pleas).  First  American  from  the  Ninth  English  Edition,  as  published 
by  the  Manchester  Reciprocity  Association.  In  one  volume,  12mo. 
Paper,  75  cts.    Cloth  $1.25 

BYRN.— The  Complete  Practical  Brewer : 

Or  Plain,  Accurate,  and  Thorough  Instructions  in  the  Art  of  Brewing 
Beer,  Ale,  Porter,  including  the  Process  of  making  Bavarian  Beer, 
all  the  Small  Beers,  such  as  Root-beer,  Ginger-pop,  Sarsaparilla- 
beer,  Mead,  Spruce  Beer,  etc.,  etc.  Adapted  to  the  use  of  Public 
Brewers  and  Private  Families.  By  M.  La  Fayette  Byrn,  M.  D. 
With  illustrations.    12mo  $1.25 


6 


HENHY  CAREY  BAIRD'S  CATALOGUE. 


BYRN.— The  Complete  Practical  Distiller : 

Comprising  the  most  perfect  and  exact  Theoretical  and  Practical  De- 
scription of  the  Art  of  Distillation  and  Rectification  ;  including  all  of 
the  most  recent  improvements  in  distilling  apparatus;  instructions 
for  preparing  spirits  from  the  numerous  vegetables,  fruits,  etc. ;  direc- 
tions for  the  distillation  and  preparation  of  all  kinds  of  brandies  and 
other  spirits,  spirituous  and  other  compounds,  etc.,  etc.  By  M.  La 
Fayette  Byrn,  M.  D.  Eighth  Edition.  To  which  are  added,  Prac- 
tical Directions  for  Distilling,  from  the  French  of  Th.  Fling,  Brewer 
and  Distiller.    12mo  $1.50 

BYRNE. — Handbook  for  the  Artisan,  Mechanic,  and 
Engineer : 

Comprising  the  Grinding  and  Sharpening  of  Cutting  Tools,  Abrasive 
Processes,  Lapidary  Work,  Gem  and  Glass  Engraving,  Varnishing 
and  Lackering,  Apparatus,  Materials  and  Processes  for  Grinding  and 
Polishing,  etc.  By  Oliver  Byrne.  Illustrated  by  185  wood  en- 
gravings.   In  one  volume,  8vo  $5.00 

BYRNE— Pocket  Book  for  Railroad  and  Civil  Engi- 
neers : 

Containing  New,  Exact,  and  Concise  Methods  for  Laying  out  Rail- 
road Curves,  Switches,  Frog  Angles,  and  Crossings ;  the  Staking 
out  of  work ;  Levelling ;  the  Calculation  of  Cuttings ;  Embankments ; 
Earth-work,  etc.  By  Oliver  Byrne.  18mo.,  full  bound,  pocket- 
book  form  $1.75 

BYRNE.— The  Practical  Model  Calculator : 

For  the  Engineer,  Mechanic,  Manufacturer  of  Engine  Work,  Naval 
Architect,  Miner,  and  Millwright.  By  Oliver  Byrne.  1  volume, 
8vo.,  nearly  600  pages  $4.50 

BYRNE.— The  Practical  Metal- Worker's  Assistant: 

Comprising  Metallurgic  Chemistry ;  the  Arts  of  Working  all  Metals 
and  Alloys ;  Forging  of  Iron  and  Steel ;  Hardening  and  Tempering ; 
Melting  and  Mixing ;  Casting  and  Founding ;  Works  in  Sheet  Metal  ; 
The  Processes  Dependent  on  the  Ductility  of  the  Metals ;  Soldering ; 
and  the  most  Improved  Processes  and  Tools  employed  by  Metal- 
workers. With  the  Application  of  the  Art  of  Electro-Metallurgy  to 
Manufacturing  Processes ;  collected  from  Original  Sources,  and  from 
the  Works  of  Holtzapffel,  Bergeron,  Leupold,  Plumier,  Napier, 
ScofFern,  Clay,  Fairbairn,  and  others.  By  Oliver  Byrne.  A  new, 
revised,  and  improved  edition,  to  which  is  added  An  Appendix,  con- 
taining The  Manufacture  of  Russian  Sheet-Iron.  By  John 
Percy,  M.  D.,  F.R.S.  The  Manufacture  of  Malleable  Iron 
Castings,  and  Improvements  in  Bessemer  Steel.  By  A.  A. 
Fesquet,  Chemist  and  Engineer.  With  over  600  Engravings,  illus- 
trating every  Branch  of  the  Subject.    8vo  $7.00 

Cabinet  Maker's  Album  of  Furniture : 

Comprising  a  Collection  of  Designs  for  Furniture.  Illustrated  by  48 
Large  and  Beautifully  Engraved  Plates.  In  one  vol.,  oblong  $5.00 


HENRY  CAREY  BAIRD'S  CATALOGUE.  7 


CALLINGHAM.— Sign  Writing  and  Glass  Emboss- 
ing: 

A  Complete  Practical  Illustrated  Manual  of  the  Art.  By  James 
Callingham.    In  one  volume,  12mo  $1.50 

CAMPIN. — A  Practical  Treatise  on  Mechanical  Engi- 
neering : 

Comprising  Metallurgy,  Moulding,  Casting,  Forging,  Tools,  Work- 
shop Machinery,  Mechanical  Manipulation,  Manufacture  of  Steam- 
engines,  etc.,  etc.  With  an  Appendix  on  the  Analysis  of  Iron  and 
Iron  Ores.  By  Francis  Campin,  C.  E.  To  which  are  added,  Obser- 
vations on  the  Construction  of  Steam  Boilers,  and  Remarks  upon 
Furnaces  used  for  Smoke  Prevention ;  with  a  Chapter  on  Explosions. 
By  R.  Armstrong,  C.  E.,  and  John  Bourne.  Rules  for  Calculating 
the  Change  Wheels  for  Screws  on  a  Turning  Lathe,  and  for  a  Wheel- 
cutting  Machine.  By  J.  La  Nicca.  Management  of  Steel,  Includ- 
ing Forging,  Hardening,  Tempering,  Annealing,  Shrinking,  and  Ex- 
pansion. And  the  Case-hardening  of  Iron.  By  G.  Ede.  8vo.  Illus- 
trated with  29  plates  and  100  wood  engravings      .       .       .  $6.00 

CAMPIN— The  Practice  of  Hand-Turning  in  Wood, 
Ivory,  Shell,  etc. : 

With  Instructions  for  Turning  such  works  in  Metal  as  may  be  re- 
quired in  the  Practice  of  Turning  Wood,  Ivory,  etc.  Also,  an  Appen- 
dix on  Ornamental  Turning.  By  Francis  Campin  ;  with  Numerous 
Illustrations.    12mo.,  cloth  $3.00 

CAREY— The  Works  of  Henry  C.  Carey : 

FINANCIAL  CRISES,  their  Causes  and  Effects.  8vo.  paper  .  25 
HARMONY  OF  INTERESTS:  Agricultural,  Manufacturing,  and 

Commercial.   8vo.,  cloth  $1.50 

MANUAL  OF  SOCIAL  SCIENCE.  Condensed  from  Carey's  "  Prin- 
ciples of  Social  Science."  By  Kate  McKean.  1  vol.  12mo.  $2.25 
MISCELLANEOUS  WORKS  :  comprising  "  Harmony  of  Interests," 
"  Money,"  "  Letters  to  the  President,"  "  Financial  Crises,"  The 
Way  to  Outdo  England  Without  Fighting  Her,"  "Resources  of 
the  Union,"  "  The  Public  Debt,"  "  Contraction  or  Expansion  ?  " 
"Review  of  the  Decade  1857-  67,"  "Reconstruction,"  etc.,  etc. 

Two  vols.,  8vo.,  cloth  $10.00 

PAST,  PRESENT,  AND  FUTURE.    8vo  $2.50 

PRINCIPLES  OF  SOCIAL  SCIENCE.    3  vols.,  8vo.,  cloth  $10.00 
THE  SLAVE-TRADE,  DOMESTIC  AND  FOREIGN ;  Why  it  Ex- 
ists,  and  How  it  may  be  Extinguished  (1853).  8vo.,  cloth    .  $2.00 
LETTERS  ON  INTERNATIONAL  COPYRIGHT  (1867)      .  50 
THE  UNITY  OF  LAW :  As  Exhibited  in  the  Relations  of  Physical, 
Social,  Mental,  and  Moral  Science  (1872).    In  one  volume,  8vo., 
pp.  xxiii.,  433.    Cloth  $3.50 

CHAPMAN.— A  Treatise  on  Ropemaking : 

As  Practised  in  private  and  public  Rope  yards,  with  a  Description 
of  the  Manufacture,  Rules,  Tables  of  Weights,  etc.,  adapted  to  the 
Trades,  Shipping,  Mining,  Railways,  Builders,  etc.  By  Robert 
Chapman.  24mo  $1.50 


8 


HENRY  CAREY  BAIRD'S  CATALOGUE. 


COLBURN— The  Locomotive  Engine  : 

Including  a  Description  of  its  Structure,  Rules  for  Estimating  its  Capa- 
bilities, and  Practical  Observations  on  its  Construction  and  Manage- 
ment. By  Zeeah  COLBUEN.  Illustrated.  A  new  edition.  12mo.  $1.25 

CRAIK.  —  The   Practical  American  Millwright  and 
Miller. 

By  David  Ceaik,  Millwright.  Illustrated  by  numerous  wood  en- 
gravings, and  two  folding  plates.    8vo  $5.00 

DE  GRAFF.— The  Geometrical  Stair  Builders'  Guide : 

Being  a  Plain  Practical  System  of  Hand-Railing,  embracing  all  its 
necessary  Details,  and  Geometrically  Illustrated  by  22  Sieel  Engrav- 
ings ;  together  with  the  use  of  the  most  approved  principles  of  Prac- 
tical Geometry.    By  Simon  De  Geaff,  Architect.   4to.      ,  $5.00 

DE  KONINCK.—DIETZ.— A  Practical  Manual  of  Che- 
mical Analysis  and  Assaying : 

As  applied  to  the  Manufacture  of  Iron  from  its  Ores,  and  to  Cast  Iron, 
Wrought  Iron,  and  Steel,  as  found  in  Commerce.  By  L.  L.  De  Kon- 
INCK,  Dr.  Sc.,  and  E.  DiETZ,  Engineer.  Edited  with  Notes,  by  Robeet 
Mallet,  F.R.S.,  F.S.G.,  M.I.C.E.,  etc.  American  Edition,  Edited 
with  Notes  and  an  Appendix  on  Iron  Ores,  by  A.  A.  Fesquet,  Chemist 
and  Engineer.    One  volume,  12mo.  $2.50 

DUNCAK.— Practical  Surveyor's  Guide: 

Containing  the  necessary  information  to  make  any  person,  of  common 
capacity,  a  finished  land  surveyor  without  the  aid  of  a  teacher.  By 
Andeew  Duncan.   Illustrated.   12mo.,  cloth.    .      .      .  $1.25 

DUPLAIS.— A  Treatise  on  the  Manufacture  and  Dis- 
tillation of  Alcoholic  Liquors : 

Comprising  Accurate  and  Complete  Details  in  Regard  to  Alcohol  from 
Wine,  Molasses,  Beets,  Grain,  Rice,  Potatoes,  Sorghum,  Asphodel, 
Fruits,  etc.  ;  with  the  Distillation  and  Rectification  of  Brandy,  Whis- 
key, Rum,  Gin,  Swiss.  Absinthe,  etc.,  the  Preparation  of  Aromatic  Wa- 
ters, Volatile  Oils  or  Essences,  Sugars,  Syrups,  Aromatic  Tinctures, 
Liqueurs,  Cordial  Wines,  Effervescing  Wines,  etc.,  the  Aging  of  Brandy 
and  the  Improvement  of  Spirits,  with  Copious  Directions  and  Tables 
for  Testing  and  Reducing  Spirituous  Liquors,  etc.,  etc.  Translated 
and  Edited  from  the  French  of  MM.  Duplais,  Aine  et  Jeune.  By 
M.  McKennie,  M.D.  To  which  are  added  the  United  States  Internal 
Revenue  Regulations  for  the  Assessment  and  Collection  of  Taxes  on 
Distilled  Spirits,  Illustrated  by  fourteen  folding  plates  and  several 
wood  engravings.    743  pp.,  8vo  $10.00 

DUSSAUCE.— A  General  Treatise  on  the  Manufacture 
of  Every  Description  of  Soap : 

Comprising  the  Chemistry  of  the  Art,  with  Remarks  on  Alkalies,  Sa- 
ponifiable  Fatty  Bodies,  the  apparatus  necessary  in  a  Soap  Factory, 
Practical  Instructions  in  the  manufactiare  of  the  various  kinds  of  Soap, 
the  assay  of  Soaps,  etc.,  etc.  Edited  from  Notes  of  Larme,  Fontenelle, 
Malapayre,  Dufour,  and  others,  with  large  and  important  additions  by 
Prof.  H.  DusSAiJCE,  Chemist.  Illustrated.  In  one  vol.,  8vo.    .  $10.00 


HENRY  CAEEY  BAIRD'S  CATALOGUE. 


9 


BUSSAUCE.— A  General  Treatise  on  the  Manufacture 
of  Vinegar : 

Theoretical  and  Practical.  Comprising  the  various  Methods,  by  the 
Slow  aud  the  Quick  Processes,  with  Alcohol,  Wine,  Grain,  Malt,  Cider, 
Molasses,  and  Beets  ;  as  well  as  the  Fabrication  of  Wood  Vinegar,  etc., 
eic.    By  Prof.  H.  Dussauce.    In  one  volume,  8vo.     .       .  $5.00 

DUSSAUCE.— A  New  and  Complete  Treatise  on  the 
Arts  of  Tanning,  Currying,  and  Leather  Dressing : 

Comprising  all  the  Discoveries  and  Improvements  made  in  France, 
Great  Britain,  and  the  United  States.  Edited  from  Notes  and  Docu- 
ments of  Messrs.  Sallerou,  Grouvelle,  Duval,  Dessables,  Labarraque, 
Payen,  Rene,  De  Fontenelle,  Malapeyre,  etc.,  etc.  By  Prof.  H.  Dus- 
SAUCE,  Chemist.    Illustrated  by  212  wood  engravings.    8vo.  $20.00 

DUSSAUCE.— A  Practical  Guide  for  the  Perfumer  : 

Being  a  New  Treatise  on  Perfumery,  the  most  favorable  to  the  Beauty 
without  being  injurious  to  the  Health,  comprising  a  Description  of  the 
.substances  used  in  Perfumery,  the  Formulse  of  more  than  1000  Prepa- 
rations, such  as  Cosmetics,  Perfumed  Oils,  Tooth  Powders,  Waters, 
Extracts,  Tinctures,  Infusions,  Spirits,  Vinaigres,  Essential  Oils,  Pas- 
tels, Creams,  Soaps,  and  many  new  Hygienic  Products  not  hitherto 
described.  Edited  from  Notes  and  Documents  of  Messrs.  Debay,  Ln- 
nel,  etc.  With  additions  by  Prof  H.  Dussauce,  Chemist.  12mo.  $3.00 

DUSSAUCE.— Practical  Treatise  on  the  Fabrication 
of  Matches,  Gun  Cotton,  and  Fulminating  Powders. 

By  Prof.  H.  DusSAUCK    12mo  $3-00 

Dyer  and  Color-maker's  Companion: 

Containing  upwards  of  200  Receipts  for  making  Colors,  on  the  most 
approved  principles,  for  all  the  various  styles  and  fabrics  now  in  exist- 
ence ;  with  the  Scouring  Process,  and  plain  Directions  for  Preparing, 
Washing-ofF,  and  Finishing  the  Goods.    In  one  vol.,  12mo.     .  $1.25 

EASTON.— A  Practical  Treatise  on  Street  or  Horse- 
power Railways. 

By  Alexander  Easton,  C.  E.  Illustrated  by  23  plates.  8vo., 
cloth  $2,00 

ELDER.— Questions  of  the  Day: 

Economic  and  Social.    By  Dr.  William  Eldee.   8vo.      .  $3.00 

FAIRBAIRW.— The  Principles  of  Mechanism  and  Ma- 
chinery of  Transmission : 

Comprising  the  Principles  of  Mechanism,  Wheels,  and  Pulleys, 
Strength  and  Proportions  of  Shafts,  Coupling  of  Shafts,  and  Engaging 
and  Disengaging  Gear.  By  Sir  William  Fairbairn,  C.E.,  LL.D., 
F.R.S.,  F.G.S.  Beautifully  illustrated  by  over  150  wood-cuts.  In 
one  volume,  12mo  $2.50 

PORSYTH.— Book  of  Designs  for  Headstones,  Mural, 
and  other  Monuments : 

Containing  78  Designs.  By  James  Forsyth.  With  an  Introduction 
by  Charles  Boutell,  M.  A.  4to.,  cloth.    ....  $5.00 


10  HENRY  CAREY  BAIRD'S  CATALOGUE, 


GIBSON.— The  American  Dyer: 

A  Practical  Treatise  on  the  Coloring  of  Wool,  Cotton,  Yarn  and 
Cloth,  in  three  parts.  Part  First  gives  a  descriptive  account  of  the 
Dye  Stuffs;  if  of  vegetable  origin,  where  produced,  how  cultivated, 
and  how  prepared  for  use ;  if  chemical,  their  composition,  specific 
gravities,  and  general  adaptability,  how  adulterated,  and  how  to  de- 
tect the  adulterations,  etc.  Part  Second  is  devoted  to  the  Coloring  of 
Wool,  giving  recipes  for  one  hundred  and  twenty-nine  different  colors 
or  shades,  and  is  supplied  with  sixty  colored  samples  of  Wool,  Part 
Third  is  devoted  to  the  Coloring  of  Raw  Cotton  or  Cotton  Waste,  for 
mixing  with  Wool  Colors  in  the  Manufacture  of  all  kinds  of  Fabrics, 
gives  recipes  for  thirty-eight  different  colors  or  shades,  and  is  supjjlied 
with  twenty-four  colored  samples  of  Cotton  Waste.  Also,  recipes  for 
Coloring  Beavers,  Doeskins,  and  Flannels,  with  remarks  upon  Ani- 
lines, giving  recipes  for  ffteen  different  colors  or  shades,  and  nine 
samples  of  Aniline  Colors  that  will  stand  both  the  Fulling  and  Scour- 
ing process.  Also,  recipes  for  Aniline  Colors  on  Cotton  Thread,  and 
recipes  for  Common  Colors  on  Cotton  Yarns.  Embracing  in  all  over 
two  hundred  recipes  for  Colors  and  Shades,  and  ninety-four  samples 
of  Colored  Wool  and  Cotton  Waste,  etc.  By  Richard  H.  Gibson,. 
Practical  Dyer  and  Chemist.    In  one  volume,  8vo.    .       .  $12.50 

GILBART.— History  and  Principles  of  Banking : 

A  Practical  Treatise.  By  James  W.  Gilbaet,  late  Manager  of  the 
London  and  Westminster  Bank.  With  additions.  In  one  volume^ 
8vo.,  600  pages,  sheep  $5.00 

Gothic  Album  for  Cabinet  Makers : 

Comprising  a  Collection  of  Designs  for  Gothic  Furniture.  Illustrated 
by  23  large  and  beautifully  engraved  plates.   Oblong  .      .  $3.00 

GRANT.  —  Beet-root  Sugar  and  Cultivation  of  the 
Beet. 

By  E.  B.  Grant.   12mo  $1.25 

GREGORY.— Mathematics  for  Practical  Men : 

Adapted  to  the  Pui'suits  of  Surveyors,  Architects,  Mechanics,  and 
Civil  Engineers.  By  Olinthus  Gregory.  8vo.,  plates,  cloth  $3.00 

GRISWOLD.— Railroad  Engineer's  Pocket  Compan- 
ion for  the  Field : 

Comprising  Rules  for  Calculating  Deflection  Distances  and  Angles^ 
Tangential  Distances  and  Angles,  and  all  Necessary  Tables  for  Engi- 
neers ;  also  the  art  of  Levelling  from  Preliminary  Survey  to  the  Con- 
struction of  Railroads,  intended  Expressly  for  the  Young  Engineer, 
together  with  Numerous  Valuable  Rules  and  Examples.  By  W. 
Grisv^^old.     12mo.,  tucks  $1.75 

GRUNER.— Studies  of  Blast  Furnace  Phenomena. 

By  M.  L.  Gruner,  President  of  the  General  Council  of  Mines  of 
France,  and  lately  Professor  of  Metallurgy  at  the  Ecole  des  Mines. 
Translated,  with  the  Author's  sanction,  with  an  Appendix,  by  L.  D.  B. 
Gordon,  F.  R.  S.  E.,  F.  G.  S.    Illustrated.    8vo.     .      .      .  $2.50 


HENRY  CAREY  BAIRD'S  CATALOGUE. 


11 


GUETTIER.— Metallic  Alloys: 

Being  a  Practical  Guide  to  their  Chemical  and  Physical  Properties, 
their  Preparation,  Composition,  and  Uses.  Translated  from  the 
French  of  A.  Gcjettier,  Engineer  and  Director  of  Foundries,  author 
of  "  La  Fouderie  en  France,"  etc.,  etc.  By  A.  A.  Fesquet,  Chemist 
and  Engineer.    In  one  volume,  12mo  $3.00 

HARRIS. — Gas  Superintendent's  Pocket  Companion. 

By  Harris  &  Brother,  Gas  Meter  Manufacturers,  1115  and  1117 
Cherry  Street,  Philadelphia.  Full  bound  in  pocket-book  form  $2.00 

Hats  and  Felting: 

A  Practical  Treatise  on  their  Manufacture.  By  a  Practical  Hatter. 
Illustrated  by  Drawings  of  Machinery,  etc.  8vo.  .      ,       .  $1.25 

HOFMANN. — A  Practical  Treatise  on  the  Manufac- 
ture of  Paper  in  all  its  Branches. 

By  Carl  Hofmann.  Late  Superintendent  of  paper  mills  in  Ger- 
many and  the  United  States ;  recently  manager  of  the  Public  Ledger 
Paper  Mills,  near  Elkton,  Md.  Illustrated  by  110  wood  engravings, 
and  five  large  folding  plates.  In  one  volume,  4to.,  <;loth;  398 
pages  $15.00 

HUGHES.— American  Miller  and  Millwright's  Assist- 
ant. 

By  Wm.  Carter  Hughes.  A  new  edition.  In  one  vol.,  12mo,  $1.50 

HURST.— A  Hand-Book  for  Architectural  Surveyors 
and  others  engaged  in  Building: 

Containing  Formulse  useful  in  Designing  Builder's  work.  Table  of 
Weights,  of  the  materials  used  in  Building,  Memoranda  connected 
with  Builders'  work.  Mensuration,  the  Practice  of  Builders'  Measure- 
ment, Contracts  of  Labor,  Valuation  of  Property,  Summarv  of  the 
Practice  in  Dilapidation,  etc.,  etc.  By  J.  F.  Hurst,  C.  E. '  Second 
edition,  pocket-book  form,  full  bound  '  $2.50 

JERVIS.— Railway  Property : 

A  Treatise  on  the  Construction  and  Management  of  Railways ;  de- 
signed to  afford  useful  knowledge,  in  the  popular  style,  to  the  holders 
of  this  class  of  property ;  as  well  as  Railway  Managers,  Officers,  and 
Agents.  By  John  B.  Jervis,  late  Chief  Engineer  of  the  Hudson 
River  Railroad,  Croton  Aqueduct,  etc.  In  one  vol.,  12mo.,  cloth  $2.00 

JOHNSTON.— Instructions  for  the  Analysis  of  Soils, 
Limestones,  and  Manures. 

By  J.  F.  W.  Johnston.   12mo  38 


12  HENKY  CAREY  BAIRIVS  CATALOGUE. 


KEENE— A  Hand-Book  of  Practical  Gauging : 

For  the  Use  of  Beginners,  to  which  is  added,  A  Chapter  on  Distilla- 
tion, describing  the  process  in  operation  at  the  Custona  House  foi^ 
ascertaining  the  strength  of  wines.  By  James  B.  Keene,  of  H.  M. 
Customs.    8vo  $1.25 

KELIjEY.— Speeches,  Addresses,  and  Letters  on  In« 
dustrial  and  Financial  Questions. 
By  Hon.  William  D.  Kelley,  M.  C.   In  one  volume,  544  pages, 
8vo.  $3.00 

KENTISH.— A  Treatise  on  a  Box  of  Instruments, 

And  the  Slide  Rule;  with  the  Theory  of  Trigonometry  and  Loga- 
rithms, including  Practical  Geometry,  Surveying,  Measuring  of  Tim- 
ber, Cask  and  Malt  Gauging,  Heights,  and  Distances.  By  Thomas 
Kentish.   In  one  volume.   12mo.       .....  $1.25 

KOBELL.—ERNI.— Mineralogy  Simplified : 

A  short  Method  of  Determining  and  Classifying  Minerals,  by  means; 
of  simple  Chemical  Experiments  in  the  Wet  Way.  Translated  from 
the  last  German  Edition  of  F.  VON  Kobell,  with  an  Introduction  tO' 
Blow-pipe  Analjrsis  and  other  additions.  By  Henei  Erni,  M.  D., 
late  Chief  Chemist,  Department  of  Agriculture,  author  of  "  Coal  Oil 
and  Petroleum."    In  one  volume,,  12mo.       ....  $2.50 

LANDRIN.— A  Treatise  on  Steel : 

Comprising  its  Theory,  Metallurgy,  Properties,  Practical  Working, 
and  Use.  By  M.  H..  C.  Landrin,  Jr.,  Civil  Engineer.  Translated 
from  the  French,  with  Notes,  by  A.  A.  Fesquet,  Chemist  and  Engi- 
neer. With  an  Appendix  on  the  Bessemer  and  the  Martin  Processes 
for  Manufacturing  Steel,  from  the  Report  of  Abram  S.  HcAvitt,  United 
States  Commissioner  to  the  Universal  Exposition,  Paris,  1867.  In  one 
volume,  12mo.   $3.00 

LARKIN. — ^The  Practical  Brass  and  Iron  Founder's 
Guide : 

A  Concise  Treatise  on  Brass  Founding,  Moulding,  the  Metals  and  their 
Alloys,  etc. :  to  which  are  added  Recent  Improvements  in  the  Manu- 
facture of  Iron,  Steel  by  the  Bessemer  Process,  etc.,  etc.  By  James 
Larkin,  late  Conductor  of  the  Brass  Foundry  Department  in  Reany, 
Neatie  &  Co's.  Penn  Works,  Philadelphia.  Fifth  edition,  revised,, 
with  Extensive  additions..   In  one  volume,  12mo.        ,      .  $2.25 


LEA VITT.— Pacts  about  Peat  as  an  Article  of  Fuel : 

With  Remarks  upon  its  Origin  and  Composition,  the  Localities  in 
which  it  is  found,  the  Methods  of  Preparation  and  Manufacture,,  and 
the  various  Uses  to  which  it  is  applicable  ;  together  with  many  other 
matters  of  Practical  and  Scientific  Interest..  To  which  is  added  a  chap- 
ter on  the  Utilization  of  Coal  Dust  with  Peat  for  the  Production  of  an 
Excellent  Fuel  at  Moderate  Cost,  specially  adapted  for  Steam  Service. 
By  T.  H.  Leavitt.   Third  edition.   12mo.         ....      $1 J5 


HENRY  CAREY  BAIRD'S  CATALOGUE. 


13 


LEROUX,  C— A  Practical  Treatise  on  the  Manufac- 
ture of  Worsteds  and  Carded  Yarns : 

Comprising  Practical  Mechanics,  with  Rules  and  Calculations  applied 
to  Spinning ;  Sorting,  Cleaning,  and  Scouring  Wools ;  the  English 
and  French  methods  of  Combing,  Drawing,  and  Spinning  Worsteds 
and  Manufacturing  Carded  Yarns.  Translated  from  the  French  of 
Charles  Leroux,  Mechanical  Engineer,  and  Superintendent  of  a 
Spinning  Mill,  by  HoRATio  Paine,  M.  D.,  and  A.  A.  Fesquet, 
Chemist  and  Engineer.  Illustrated  by  12  large  Plates.  To  which  is 
added  an  Appendix,  containing  extracts  from  the  Reports  of  the  Inter- 
national Jury,  and  of  the  Artisans  selected  by  the  Committee  appointed 
by  the  Council  of  the  Society  of  Arts,  London,  on  Woollen  and  Worsted 
Machinery  and  Fabrics,  as  exhibited  in  the  Paris  Universal  Exposi- 
tion, 1867.    8vo.,  cloth   $5.00 

LESLIE  (Miss).— Complete  Cookery: 

Directions  for  Cookery  in  its  Various  Branches.  By  MiSS  Leslie. 
60th  thousand.  Thoroughly  revised,  with  the  addition  of  New  Re- 
ceipts.   In  one  volume,  12mo.,  cloth  $1.50 

LESLIE  (Miss).— Ladies'  House  Book: 

A  Manual  of  Domestic  Economy.    20th  revised  edition.    12mo.,  cloth. 

LESLIE  (Miss).— Two  Hundred  Receipts  in  French 
Cookery. 

Cloth,  12mo. 

LIEBER.— Assayer's  Guide : 

Or,  Practical  Directions  to  Assayers,  Miners,  and  Smelters,  for  the 
Tests  and  Assays,  by  Heat  and  by  Wet  Processes,  for  the  Ores  of  all 
the  principal  Metals,  of  Gold  and  Silver  Coins  and  Alloys,  and  of 
Coal,  etc.    By  Oscar  M.  Lieber.    12mo.,  cloth.        .      .  $1.25 

LOTH.— The  Practical  Stair  Builder : 

A  Complete  Treatise  on  the  Art  of  Building  Stairs  and  Hand-Rails, 
Designed  for  Carpenters,  Builders,  and  Stair-Builders.  Illustrated 
with  Thirty  Original  Plates.  By  C.  Edward  Loth,  Professional 
Stair-Builder.    One  large  4to.  volume.        ....  $10.00 

LOVE.— The  Art  of  Dyeing,  Cleaning,  Scouring,  and 
Finishing,  on  the  Most  Approved  English  and 
French  Methods: 

Being  Practical  Instructions  in  Dyeing  Silks,  Woollens,  and  Cottons, 
Feathers,  Chips,  Straw,  etc.  Scouring  and  Cleaning  Bed  and  Window 
Curtains,  Carpets,  Rugs,  etc.  French  and  English  Cleaning,  any 
Color  or  Fabric  of  Silk,  Satin,  or  Damask.  By  Thomas  Love,  a 
Working  Dyer  and  Scourer.  Second  American  Edition,  to  which  are 
added  General  Instructions  for  the  Use  of  Aniline  Colors.  In  one 
volume,  8vo,,  343  pages.  $5.00 


14  HENRY  CAREY  BAIRD'S  CATALOGUE. 


MAIN  and  BROWN.— Questions  on  Subjects  Con- 
nected with  the  Marine  Steam-Engine : 

And  Examination  Papers ;  with  Hints  for  their  Solution.  By  Thomas 
J.  Main,  Professor  of  Mathematics,  Royal  Naval  College,  and  Thomas 
Bkown,  Chief  Engineer,  R.  N.    12mo.,  cloth.      .       .       .  $1.50 

MAIN  and  BROWN.— The  Indicator  and  Dynamo- 
meter : 

With  their  Practical  Applications  to  the  Steam-Engine.  By  Thomas 
J.  Main,  M.  A.  F.  R.,  Assistant  Professor  Royal  Naval  College,  Ports- 
mouth, and  Thomas  Brown,  Assoc.  Inst.  C.  E.,  Chief  Engineer,  R. 
N.,  attached  to  the  Royal  Naval  College.  Illustrated.  From  the 
Fourth  London  Edition.    8vo  $1.50 


MAIN  and  BROWN.— The  Marine  Steam-Engine. 

By  Thomas  J.  Main,  F.  R.  ;  Assistant  S.  Mathematical  Professor  at 
the  Royal  Naval  College,  Portsmouth,  and, Thomas  Beown,  Assoc. 
Inst.  C.  E.,  Chief  Engineer  R.  N.  Attached  to  the  Royal  Naval  Col- 
lege. Authors  of  "  Questions  connected  with  the  Marine  Steam-En- 
gine," and  the  "  Indicator  and  Dynamometer."  With  numerous  Illus- 
trations.   In  one  volume,  8vo.  $5.00 


MARTIN.— Screw-Cutting  Tables,  for  the  Use  of  Me- 
chanical Engineers : 

Showing  the  Proper  Arrangement  of  Wheels  for  Cutting  the  Threads 
of  Screws  of  any  required  Pitch  ;  with  a  Table  for  Making  the  Uni- 
versal Gas-Pipe  Thread  and  Taps.  By  W.  A.  Martin,  Engineer. 
8vo  50 

Mechanics'  (Amateur)  Workshop: 

A  treatise  containing  plain  and  concise  directions  for  the  manipula- 
tion of  Wood  and  Metals,  including  Casting,  Forging,  Brazing,  Sol- 
dering, and  Carpentry.  By  the  author  of  the  "  Lathe  and  its  Uses." 
Third  edition.    Illustrated.    8vo  $3.00 


MOLESWORTH.— Pocket-Book  of  Useful  Formulas 
and  Memoranda  for  Civil  and  Mechanical  Engi- 
neers. 

By  Guilford  L.  Molesworth,  Member  of  the  Institution  of  Civil 
Engineers,  Chief  Resident  Engineer  of  the  Ceylon  Railway.  Second 
American,  from  the  Tenth  London  Edition.  In  one  volume,  full 
bound  in  pocket-book  form  $2.00 


NAPIER.— A  System  of  Chemistry  Applied  to  Dyeing. 

By  James  Napier,  F.  C.  S.  A  New  and  Thoroughly  Revised  Edi- 
tion. Completely  brought  up  to  the  present  state  of  the  Science,  inclu- 
ding the  Chemistry  of  Coal  Tar  Colors,  by  A.  A.  Fesquet,  Chemist 
and  Engineer.  With  an  Appendix  on  Dyeing  and  Calico  Printing,  as 
shown  at  the  Universal  Exposition,  Paris,  1867.  Illustrated.  In  one 
volume,  8vo.,  422  pages.  .       .       .       .       .       .       .       .  $5.00 


HENRY  CAREY  BAIRD'S  CATALOGUE.  15 


NAPIER— Manual  of  Electro-Metallurgy : 

Including  the  Application  of  the  Art  to  Manufacturing  Processes.  By 
James  Napier,  Fourth  American,  from  the  Fourth  London  edition, 
revised  and  enlarged.  Illustrated  by  engravings.  In  one  vol.,  8vo.  |2.00 

NASON.— Table  of  Reactions  for  Qualitative  Chemical 
Analysis. 

By  Henry  B.  Nason,  Professor  of  Chemistry  in  the  Rensselaer  Poly- 
technic Institute,  Troy,  New  York.    Illustrated  by  Colors.      .  63 

NEWBERY.— Gleanings    from   Ornamental  Art  of 
every  style : 

Drawn  from  Examples  in  the  British,  South  Kensington,  Indian, 
Crystal  Palace,  and  other  Museums,  the  Exhibitions  of  1851  and  1862, 
and  the  best  English  and  Foreign  works.  In  a  series  of  one  hundred 
exquisitely  drawn  Plates,  containing  many  hundred  examples.  By 
Robert  Newbery.   4to  $15.00 

NICHOLSON— A  Manual  of  the  Art  of  Bookbinding : 

Containing  full  instructions  in  the  different  Branches  of  Forwarding, 
Gilding,  and  Finishing.  Also,  the  Art  of  Marbling  Book-edges  and 
Paper.   By  James  B.  Nicholson.   Illustrated.   12mo.,  cloth.  $2.25 

NICHOLSON— The  Carpenter's  New  Guide: 

A  Complete  Book  of  Lines  for  Carpenters  and  Joiners.  By  Peter 
Nicholson.  The  whole  carefully  and  thoroughly  revised  by  H.  K. 
Davis,  and  containing  numerous  new  and  improved  and  original  De- 
signs for  Roofs,  Domes,  etc.  By  Samuel  Sloan,  Architect.  Illus- 
trated by  80  plates.    4to  $4.50 

NORRIS.— A  Hand-book  for  Locomotive  Engineers 
and  Machinists: 

Comprising  the  Proportions  and  Calculations  for  Constructing  Loco- 
motives ;  Manner  of  Setting  Valves ;  Tables  of  Squares,  Cubes,  Areas, 
etc.,  etc.  By  Septimus  Norris,  Civil  and  Mechanical  Engineer. 
New  edition.    Illustrated.    12mo.,  cloth  $2.00 

NYSTBOM.— On  Technological  Education,  and  the 
Construction  of  Ships  and  Screw  Propellers : 

For  Naval  and  Marine  Engineers.  By  John  W.  Nystrom,  late  Act- 
ing Chief  Engineer,  U.  S.  N.  Second  edition,  revised  with  additional 
matter.    Illustrated  by  seven  engravings.    12mo.        .       .  $1.50 

O'NEILL— A  Dictionary  of  Dyeing  and  Calico  Print- 
ing: 

Containing  a  brief  account  of  all  the  Substances  and  Processes  in  use 
in  the  Art  of  Dyeing  and  Printing  Textile  Fabrics;  with  Practical 
Receipts  and  Scientific  Information.  By  Charles  O'Neill,  Ana- 
lytical Chemist ;  Fellow  of  the  Chemical  Society  of  London  ;  Member 
of  the  Literarv  and  Philosophical  Society  of  Manchester  ;  Author  of 
"  Chemistry  of  Calico  Printing  and  I>yeing."  To  which  is  added  an 
Essay  on  Coal  Tar  Colors  and  their  application  to  Dyeing  and  Calico 
Printing.  By  A.  A.  Fesquet,  Chemist  and  Engineer.  With  an  Ap- 
pendix on  Dyeing  and  Calico  Printing,  as  shown  at  the  Universal 
Exposition,  Paris,  1867.   In  one  volume,  8vo.,  491  pages.    .  $6.00 


16  HENRY  CAREY  BAIRD'S  CATALOGUE. 


ORTON.— Underground  Treasures: 

How  and  Where  to  Find  Them.  A  Key  for  the  Ready  Determination 
of  all  the  Useful  Minerals  within  the  United  States.  By  James 
Orton,  a.  M.    Illustrated,  12mo  $1.50 

OSBORN.— American  Mines  and  Mining: 

Theoretically  and  PracticaUy  Considered.  By  Prof.  H.  S.  OSBORN. 
Illustrated  by  numerous  engravings.    8vo.    {In  preparation.) 

OSBORN.— The  Metallurgy  of  Iron  and  Steel : 

Theoretical  and  Practical  in  pll  its  Branches ;  with  special  reference 
to  American  Materials  and  Processes.  By  H.  S.  Oscorn,  LL.  D., 
Professor  of  Mining  and  Metallurgy  in  Lafayette  College,  Easton, 
Pennsylvania.  Illustrated  by  numerous  large  folding  plates  and 
wood-engravings.    8vo.  $15.00 

OVERMAN— The  Manufacture  of  Steel : 

Containing  the  Practice  and  Principles  of  Working  and  Making  Steel. 
A  Handbook  for  Blacksmiths  and  Workers  in  Steel  and  Iron,  Wagon 
Makers,  Die  Sinkers,  Cutlers,  and  Manufacturers  of  Files  and  Hard- 
ware, of  Steel  and  Iron,  and  for  Men  of  Science  and  Art.  By  Fred- 
erick Overman,  Mining  Engineer,  Author  of  the  "  Manufacture  of 
Iron,"  etc.  A  new,  enlarged,  and  revised  Edition.  By  A.  A.  Fesquet, 
Chemist  and  Engineer  $1.50 

OVERMAN.— The   Moulder  and  Founder's  Pocket 
Guide  : 

A  Treatise  on  Moulding  and  Founding  in  Green-sand,  Dry-sand,  Loam, 
and  Cement;  the  Moulding  of  Machine  Frames,  Mill-gear,  Hollow- 
ware,  Ornaments,  Trinkets,  Bells,  and  Statues  ;  Description  of  Moulds 
for  Iron,  Bronze,  Brass,  and  other  Metals  ;  Plaster  of  Paris,  Sulphur, 
Wax,  and  other  articles  commonly  used  in  Casting ;  the  Construction 
of  Melting  Furnaces,  the  Melting  and  Founding  of  Metals  ;  the  Com- 
position of  Alloys  and  their  Nature.  With  an  Appendix  containing 
Receipts  for  Alloys,  Bronze,  Varnishes  and  Colors  for  Castings ;  also. 
Tables  on  the  Strength  and  other  qualities  of  Cast  Metals.  By  Fred- 
erick Overman,  Mining  Engineer,  Author  of  "  The  Manufacture 
of  Iron."    With  42  Illustrations.    12mo  $1.50 

Painter,  Gilder,  and  Varnisher's  Companion : 

Containing  Rules  and  Regulations  in  everything  relating  to  the  Arts 
of  Painting,  Gilding,  Varnishing,  Glass-Staining,  Graining,  Marbling, 
Sign- Writing,  Gilding  on  Glass,  and  Coach  Painting  and  Varnishing ; 
Tests  for  the  Detection  of  Adulterations  in  Oils,  Colors,  etc. ;  and  a 
Statement  of  the  Diseases  to  which  Painters  are  peculiarly  liable,  with 
the  Simplest  and  Best  Remedies.  Sixteenth  Edition.  Revised,  with 
an  Appendix.  Containing  Colors  and  Coloring— Theoretical  and 
Practical.  Comprising  descriptions  of  a  great  variety  of  Additional 
Pigments,  their  Qualities  and  Uses,  to  which  are  added,  Dryers,  and 
Modes  and  Operations  of  Painting,  etc.  Together  with  Chevreul's 
Principles  of  Harmony  and  Contrast  of  Colors.    12mo.,  cloth.  $1.50 


Practical  Treatise  on  »jras  and  Ventilation.    With  Special  Relation  to 
Illuminating,  Heating,  and  Cooking  by  Gas.    Including  Scientific ' 
Helps  to  Engineer-students  and  others.    With  Illustrated  Diagrams. 
By  E.  E.  Perkins.  12mo-,  cloth  $1.25 

PERKINS  and  STOWE.— A  New  Guide  to  the  Sheet- 
iron  and  Boiler  Plate  Roller : 

Containing  a  Series  of  Tables  showing  the  Weight  of  Slabs  and  Piles 
to  produce  Boiler  Plates,  and  of  the  Weight  of  Piles  and  the  Sizes  of 
Bars  to  produce  Sheet-iron;  the  Thickness  of  the  Bar  Gauge  in 
decimals ;  the  Weight  per  foot,  and  the  Thickness  on  the  Bar  or  Wire 
Gauge  of  the  fractional  parts  of  an  inch  ;  the  Weight  per  sheet,  and 
the  Thickness  on  the  Wire  Gauge  of  Sheet-iron  of  various  dimensions 
to  weigh  112  lbs.  per  bundle;  and  the  conversion  of  Short  Weight 
into  Long  Weight,  and  Long  Weight  into  Short.  Estimated  and  col- 
lected by  -G.  H.  Perkins  and  J.  G.  Stowe  $2.50 

PHILLIPS  and  DARLINGTON.— Records  of  Mining 
and  Metallurgy; 

Or  Facts  and  Memoranda  for  the  use  of  the  Mine  Agent  and  Smelter. 
By  J.  Arthur  Phillips,  Mining  Engineer,  Graduate  of  the  Imperial 
School  of  Mines,  France,  etc.,  and  John  Darlington.  Illustrated 
by  numerous  engravings.    In  one  volume,  12mo,         .       .  $2.00 

PROTEAUX.— Practical  Guide  for  the  Manufacture 
of  Paper  and  Boards. 

By  A.  Proteattx,  Civil  Engineer,  and  Graduate  of  the  School  of  Arts 
and  Manufactures,  and  Director  of  Thiers'  Paper  Mill,  Puy-de-D6me. 
With  additions,  by  L.  S.  Le  Normand.  Translated  from  the  French, 
with  Notes,  by  Horatio  Paine,  A.  B.,  M.  D.  To  which  is  added  a 
Chapter  on  the  Manufacture  of  Paper  from  Wood  in  the  United 
States,  by  Henry  T.  Brow^n,  of  the  "  American  Artisan."  Illus- 
trated by  six  plates,  containing  Drawings  of  Raw  Materials,  Machi- 
nery, Plans  of  Paper-Mills,  etc.,  etc.    8vo  $7.50 

RE GNAULT.— Elements  of  Chemistry. 

By  M.  V.  Regnaijlt.  Translated  from  the  French  by  T.  Forrest 
Betton,  M.  D.,  and  edited,  with  Notes,  by  James  C.  Booth,  Melter 
and  Refiner  U.  S.  Mint,  and  Wm.  L.  Faber,  Metallurgist  and  Mining 
Engineer.  Illustrated  by  nearly  700  wood  engravings.  Comprising 
nearly  1500  pages.    In  two  volumes,  8vo.,  cloth.   .      .      ,  $7.50 


Edited  by  M.  F.  MalepeY!.^  .id  Dr.  JiMiL  v.  ijxcj:.  .^er.  Illustrated. 
In  one  volume,  8vo.    {In  preparation.) 


RIFFAULT,  VERGNAUD,  and  TOTJSSAINT.— A 
Practical  Treatise  on  the  Manufacture  of  Colors 
for  Painting: 

Containing-  the  best  Formul8&  and  the  Processes  the  Newest  and  in 
most  General  Use.  By  M  M.  Eiffault,  Vergnaud,  and  Toussaint. 
Kevised  and  Edited  by  M.  F.  Malepeyre  and  Dr.  Emil  Winckler. 
Translated  from  the  French  by  A.  A.  Fesqtjet,  Chemist  and  Engi- 
neer. Illustrated  by  Engravings.  In  one  volume^  650  pages,  8vo. 
{Ready  June  1,  1874.) 

ROBINSON— Explosions  of  Steam  Boilers: 

How  they  are  Caused,  and  how  they  may  be  Prevented.  By  J.  E. 
EOBINSON,  Steam  Engineer.   12mo.      .....  $1.25 

ROPER.— A  Catechism  of  High  Pressure  or  Non- 
Condensing  Steam-Engines : 

Including  the  Modelling,  Constructing,  Eunning,  and  Management 
of  Steam  Engines  and  Steam  Boilers.  With  Illustrations.  By 
Stephen  Eoper,  Engineer.  Full  bound  tucka  .      .      .  $2.00 

ROSELEXJR.— Galvanoplastic  Manipulations : 

A  Practical  Guide  for  the  Gold  and  Silver  Electro-plater  and  the 
Galvanoplastic  Operator.  Translated  from  the  French  of  Alfred 
EosELETJR,  Chemist,  Professor  of  the  Galvanoplastic  Art,  Manufactu- 
rer of  Chemicals,  Gold  and  Silver  Electro-plater.  By  A.  A.  Fesquet, 
Chemist  and  Engineer.   Illustrated  by  over  127  Engravings  on  wood. 

8vo.,  495  pages  $6.00 

This  Treatise  is  the  fullest  and  hy  far  the  best  on  this  subject  ever 
published  in  the  United  States. 

SCHINZ.— Researches  on  the  Action  of  the  Blast 
Furnace. 

By  Charles  Schinz.  Translated  from  the  German  with  the  special 
permission  of  the  Author  by  William  H.  Maw  and  Moritz  Mul- 
ler.  With  an  Appendix  written  by  the  Author  expressly  for  this 
edition.  Illustrated  by  seven  plates,  containing  28  figures.  In  one 
volume,  12mo.   .      .  $4.25 


HENRY  CAEEY  BAIRD'S  CATALOGUE.  19 


SHAW.— Civil  Architecture : 

Being  a  Complete  Theoretical  and  Practical  System  of  Building,  con- 
taining the  Fundamental  Principles  of  the  Art.  By  Edward  Shaw, 
Architect.  To  which  is  added  a  Treatise  on  Gothic  Architecture,  etc. 
By  Thomas  W,  Silloway  and  Geoege  M.  Harding,  Architects, 
The  whole  illustrated  by  One  Hundred  and  Two  quarto  plates  finely 
engraved  on  copper.    Eleventh  Edition.   4to.,  cloth.        .  $10,00 

SHUNK.— A  Practical  Treatise  on  Hailway  Curves 
and  Location,  for  Young  i3ngineers. 

By  William     Shtjnk,  Civil  Engineer.    12mo.       ,      ,  $2.00 

SLOAN.— American  Houses: 

A  variety  of  Original  Designs  for  Rural  Buildings.  Illustrated  by  26 
colored  Engravings,  with  Descriptive  References.  By  Samuel  Sloan, 
Architect,  author  of  the    Model  Architect,"  etc.,  etc    8vo.  $2.50 

SMEATON.— Builder's  Pocket  Companion: 

Containing  the  Elements  of  Building,  Surveying,  and  Architecture ; 
with  Practical  Rules  and  Instructions  connected  with  the  subject. 
By  A.  C,  Smeaton,  Civil  Engineer,  etc.    In  one  volume,  12ma,  $1.50 

SMITH.— A  Manual  of  Political  Economy. 

By  E.  Peshine  Smith.  A  new  Edition,  to  which  is  added  a  full 
Index.   12mo,,  cloth,      ,      ,  $1.25 

SMITH.— Parks  and  Pleasure  Grounds: 

Or  Practical  Notes  on  Country  Residences,  Villas,  Public  Parks,  and 
Gardens.  By  Charles  H.  J.  Smith,  Landscape  Gardener  and 
Garden  Architect,  etc.,  etc    12mo,  $2.25 

SMITH.— The  Dyer's  Instructor  : 

Comprising  Practical  Instructions  in  the  Art  of  Dyeing  Silk,  Cotton, 
Wool,  and  Worsted,  and  Woollen  Goods  4  containing  nearly  800 
Receipts.  To  which  is  added  a  Treatise  on  the  Art  of  Padding ;  and 
the  Printing  of  Silk  Warps,  Skeins,  and  Handkerchiefs,  and  the 
various  Mordants  and  Colors  for  the  different  styles  of  such  work. 
By  David  Smith,  Pattern  Dyer,    12mo.,  cloth,  ,      ,  .    .  $3.00 

SMITH.— The  Practical  Dyer's  Guide: 

Comprising  Practical  Instructions  in  the  Dyeing  of  Shot  Cobourgs, 
Silk  Striped  Orleans,  Colored  Orleans  from  Black  Warps,  Ditto  from 
White  Warps,  Colored  Cobourgs  from  White  Warps,  Merinos,  Yarns, 
Woollen  Cloths,  etc.  Containing  nearly  300  Receipts,  to  most  of  which 
a  Dyed  Pattern  is  annexed.  Also,  A  Treatise  on  the  Art  of  Padding. 
By  David  Smith.    In  one  volume,  8vo.    Price.       ,      ,  $25.00 

STEWART.— The  American  System. 

Speeches  on  the  Tariff  Question,  and  on  Internal  Improvements,  princi- 
pally delivered  in  the  House  of  Representatives  of  the  United  States. 
By  Andrew  Stewart,  late  M.  C.  from  Pennsylvania.  With  a  Portrait, 
and  a  Biographical  Sketch.    In  one  volume,  8vo.,  407  pages.  $3.00 


20  HENRY  CAREY  BAIRD'S  CATALOGUE. 


STOKES— Cabinet-maker's  and  Upholsterer's  Com- 
panion : 

Comprising  the  Rudiments  and  Principles  of  Cabinet-making  and  Up- 
holstery, with  Familiar  Instructions,  illustrated  by  Examples  for 
attaining  a  Proficiency  in  the  Art  of  Drawing,  as  applicable  to  Cabi- 
net-work ;  the  Processes  of  Veneering,  Inlaying,  and  Buhl-work  ;  the 
Art  of  Dyeing  and  Staining  Wood,  Bone,  Tortoise  Shell,  etc.  Direc- 
tions for  Lackering,  Japanning,  and  Varnishing;  to  make  French 
Polish ;  to  prepare  the  Best  Glues,  Cements,  and  Compositions,  and  a 
number  of  Receipts  particularly  useful  for  workmen  generally.  By 
J.  Stokes,    In  one  volume,  12mo.   With  Illustrations.      .  $1.25 

Strength  and  other  Properties  of  Metals: 

Reports  of  Experiments  on  the  Strength  and  other  Properties  of  Metals 
for  Cannon.  With  a  Description,  of  the  Machines  for  testing  Metals, 
and  of  the  Classification  of  Cannon  in  service.  By  Officers  of  the  Ord- 
nance Department  U.  S.  Army.  By  authority  of  the  Secretary  of  War. 
Illustrated  by  25  large  steel  plates.    In  one  volume,  4to.    .  $10.00 

SULLIVAIS'.— Protection  to  Wative  Industry. 

By  Sir  Edward  Sullivan,  Baronet,  author  of  "  Ten  Chapters  on 
Social  Reforms."    In  one  volume,  8vo  $1.50 

Tables  Showing  the  Weight  of  Round,  Square,  and 
Flat  Bar  Iron,  Steel,  etc., 
By  Measurement.    Cloth  65 

TAYLOR.— Statistics  of  Coal : 

Including  Mineral  Bituminous  Substances  employed  in  Arts  and 
Manufactures ;  with  their  Geographical,  Geological,  and  Commercial 
Distribution  and  Amount  of  Production  and  Consumption  on  the 
American  Continent.  With  Incidental  Statistics  of  the  Iron  Manu- 
facture. By  R.  C.  Taylor.  Second  edition,  revised  by  S.  S.  Hal- 
DEMAN.    Illustrated  by  five  Maps  and  many  wood  engravings.  Svo,,^ 

cloth  $io.oa 

TEMPLETON.— The  Practical  Examinator  on  Steam 
and  the  Steam-Engine : 

With  Instructive  References  relative  thereto,  arranged  for  the  Use  of 
Engineers,  Students,  and  others.  By  Wm.  Templeton,  Engineer. 
12mo  $1.25 

THOMAS— The  Modern  Practice  of  Photography. 

By  R.  W.  Thomas,  F.  C.  S.   8vo.,  cloth.  75 

THOMSON.— Freight  Charges  Calculator. 

By  Andrew  Thomson,  Freight  Agent.   24m o.    .      .      .  $1.25 

TURNING:  Specimens  of  Fancy  Turning  Executed 
on  the  Hand  or  Foot  Lathe; 

With  Geometric,  Oval,  and  Eccentric  Chucks,  and  Elliptical  Cutting- 
Frame.  By  an  Amateur.  Illustrated  by  30  exquisite  Photographs. 
4to.    .....   $3.00 


HENRY  CAREY  BAIRD'S  CATALOGUE. 


21 


Turner's  (The)  Companion: 
Containing  Instructions  in  Concentric,  Elliptic,  and  Eccentric  Turn- 
ing :  also  various  Plates  of  Chucks,  Tools,  and  Instruments  ;  and  Di- 
rections for  using  the  Eccentric  Cutter,  Drill,  Vertical  Cutter,  and 
Circular  Rest ;  with  Patterns  and  Instructions  for  working  them.  A 
new  edition  in  one  volume,  12mo.   $1.50 

URBIN— BRULL.— A  Practical  Guide  for  Puddling 
Iron  and  Steel. 

By  Ed.  Uebin,  Engineer  of  Arts  and  Manufactures.  A  Prize  Essay- 
read  before  the  Association  of  Engineers,  Graduate  of  the  School  of 
Mines,  of  Liege,  Belgium,  at  the  Meeting  of  1 865-6.  To  which  is  added 
A  Comparison  of  the  Resisting  Properties  of  Iron  and  Steel. 
By  A.  Brull.  Translated  from  the  French  by  A.  A.  Fesquet,  Che- 
mist and  Engineer.    In  one  volume,  8vo  $1.00 

VAILE.— Galvanized  Iron  Cornice-Worker's  Manual: 

Containing  Instructions  in  Laying  out  the  Different  Mitres,  and  Ma- 
king Patterns  for  all  kinds  of  Plain  and  Circular  Work.  Also,  Tables 
of  Weights,  Areas  and  Circumferences  of  Circles,  and  other  Matter 
calculated  to  Benefit  the  Trade.  By  Charles  A.  Vaile,  Superin- 
tendent "Richmond  Cornice  Works,"  Richmond,  Indiana.  Illustra- 
ted by  21  Plates.    In  one  volume,  4to  $5.00 

VILLE.— The  School  of  Chemical  Manures : 

Or,  Elementary  Principles  in  the  Use  of  Fertilizing  Agents.  From  the 
French  of  M.  George  Ville,  by  A.  A.  Fesquet,  Chemist  and  Engi- 
neer.   With  Illustrations.    In  one  volume,  12  mo.       .       .  $1.25 

VOGDES.— The  Architect's  and  Builder's  Pocket  Com- 
panion and  Price  Book: 

Consisting  of  a  Short  but  Comprehensive  Epitome  of  Decimals,  Duo- 
decimals, Geometry  and  Mensuration ;  with  Tables  of  U.  S.  Measures, 
Sizes,  Weights,  Strengths,  etc.,  of  Iron,  Wood,  Stone,  and  various 
other  Materials,  Quantities  of  Materials  in  Given  Sizes,  and  Dimen- 
sions of  Wood,  Brick,  and  Stone ;  and  a  full  and  complete  Bill  of 
Prices  for  Carpenter's  Work ;  also.  Rules  for  Computing  and  Valuing 
Brick  and  Brick  Work,  Stone  Work,  Painting,  Plastering,  etc.  By 
Frank  W.  Vogdes,  Architect.  Illustrated.  Full  bound  in  pocket- 
book  form  $2.00 

Bound  in  cloth.  1.50 

WARN.— The  Sheet-Metal  Worker's  Instructor: 

For  Zinc,  Sheet-Iron,  Copper,  and  Tin-Plate  Workers,  etc.  Contain- 
ing a  selection  of  Geometrical  Problems ;  also.  Practical  and  Simple 
Rules  for  describing  the  various  Patterns  required  in  the  different 
branches  of  the  above  Trades.  By  Reuben  H.  Warn,  Practical  Tin- 
plate  Worker.  To  which  is  added  an  Appendix,  containing  Instruc- 
tions for  Boiler  Making,  Mensuration  of  Surfaces  and  Solids,  Rules  for 
Calculating  the  Weights  of  different  Figures  of  Iron  and  Steel,  Tables 
of  the  Weights  of  Iron,  Steel,  etc.  Illustrated  by  32  Plates  and  37 
Wood  Engravings.    8vo.  $3.00 


22 


HENHY  CAREY  BAIRD'S  CATALOGUE. 


WARNER.— New  Theorems,  Tables,  and  Diagrams 
for  the  Computation  of  Earth- Work : 

Designed  for  the  use  of  Engineers  in  Preliminary  and  Final  Estimates, 
of  Students  in  Engineering,  and  of  Contractors  and  other  non-profes- 
sional Computers.  In  Two  Parts,  with  an  Appendix.  Part  I. — A 
Practical  Treatise  ;  Part  II. — A  Theoretical  Treatise ;  and  the  Appen- 
dix. Containing  Notes  to  the  Rules  and  Examples  of  Part  I. ;  Expla- 
nations of  the  Construction  of  Scales,  Tables,  and  Diagrams,  and  a 
Treatise  upon  Equivalent  Square  Bases  and  Equivalent  Level  Heights. 
The  whole  illustrated  by  numerous  original  Engravings,  comprising 
Explanatory  Cuts  for  Definitions  and  Problems,  Stereometric  Scales 
and  Diagrams,  and  a  Series  of  1  ithographic  Drawings  from  Models, 
showing  all  the  Combinations  of  Solid  Forms  which  occur  in  Railroad 
Excavations  and  Embankments.  By  JOHN  WARNER,  A.  M.,  Mining 
and  Mechanical  Engineer.    8vo  $5.00 

WATSON.— A  Manual  of  the  Hand-Lathe : 

Comprising  Concise  Directions  for  working  Metals  of  all  kinds,  Ivory, 
Bone  and  Precious  Woods ;  Dyeing,  Coloring,  and  French  Polishing ; 
Inlaying  by  Veneers,  and  various  methods  practised  to  produce  Elabo- 
rate work  with  Dispatch,  and  at  Small  Expense.  By  Egbert  P. 
Watson,  late  of  "  The  Scientific  American,"  Author  of  "  The  Modern 
Practice  of  American  Machinists  and  Engineers."    Illustrated  by  78 


WATSON.— The  Modern  Practice  of  American  Ma- 
chinists and  Engineers: 

Including  the  Construction,  Application,  and  Use  of  Drills,  Lathe 
Tools,  Cutters  for  Boring  Cylinders,  and  Hollow  Work  Generally, 
with  the  most  Economical  Speed  for  the  same  ;  the  Results  verified  by 
Actual  Practice  at  the  Lathe,  the  Vice,  and  on  the  Floor.  Together 
with  Workshop  Management,  Economy  of  Manufacture,  the  Steam- 
Engine,  Boilers,  Gears,  Belting,  etc.,  etc.  By  Egbert  P.  Watson, 
late  of  the  "  Scientific  American."    Illustrated  by  86  Engravings.  In 


WATSON.— The  Theory  and  Practice  of  the  Art  of 
Weaving  by  Hand  and  Power : 

With  Calculations  and  Tables  for  the  use  of  those  connected  with  the 
Trade.  By  John  Watson,  Manufacturer  and  Practical  Machine 
Maker.  Illustrated  by  large  Drawings  of  the  best  Power  Looms. 
8vo  $10.00 

WEATHERLY.— Treatise  on  the  Art  of  Boiling  Su- 
gar, Crystallizing,  Lozenge-making,  Comfits,  Gum 
Goods. 

12mo  $2.00 

WEDDING.— The  Metallurgy  of  Iron; 

Theoretically  and  Practically  Considered.  By  Dr.  Hermann  Wed- 
ding, Professor  of  the  Metallurgy  of  Iron  at  the  Royal  Mining 
Academy,  Berlin.  Translated  by  Julius  Du  Mont,  Bethlehem,  Pa. 
Illustrated  by  207  Engravings  on  Wood,  and  three  Plates.  In  one 
volume,  8vo.    {In  press.) 


Engravings. 


$1.50 


one  volume,  12mo. 


$2.50 


IIENKY  CAREY  BAIRD'S  CATALOGUE. 


23 


"WILL. — Tables  for  Qualitative  Chemical  Analysis. 

By  Professor  Heinrich  Will,  of  Giessen,  Germany.  Seventh  edi- 
tion. Translated  by  Charles  F.  Himes,  Ph.  D.,  Professor  of  Natu- 
ral Science,  Dickinson  College,  Carlisle,  Pa. 

"WILLIAMS.— On  Heat  and  Steam : 

Embracing  New  Views  of  Vaporization,  Condensation,  and  Explosions. 
By  Charles  Wye  Williams,  A.  I.  C.  E.   Illustrated.   8vo.  $3.50 

"WOHLER.— A  Hand-Book  of  Mineral  Analysis. 

By  F.  WOHLER,  Professor  of  Chemistry  in  the  University  of  Gottin- 
gen.  Edited  by  Henry  B.  Nason,  Professor  of  Chemistry  in  the 
Rensselaer  Polytechnic  Institute,  Troy,  New  York.  Illustrated.  In 
one  volume,  12mo  $3. 00 

"WORSSAM.— On  Mechanical  Saws: 

From  the  Transactions  of  the  Society  of  Engineers,  1869.  By  S.  W. 
WOESSAM,  Jr.   Illustrated  by  18  large  plates.   8vo.    .      .  $5.00 


m. 


